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Blood sampling typically involves puncturing a superficial vein with a needle and then creating a vacuum (e. g., with a syringe) to transfer the blood from the venous system to the collection container. In some cases, the venous walls collapse due to excessive vacuum generated. In this work, a device is presented that prevents venous collapse and can be combined with any blood collection system available on the market. The mechanism of preventing venous collapse is based on a tubular segment interconnected between the needle and the syringe, which collapses at a lower vacuum pressure than the vein. The prototype was tested and evaluated using a test rig that simulates venous blood draw. The experiments proved the functionality of the device on a vein phantom.

In this work, an electrode was developed to determine the dielectric properties of tissue phantoms using impedance measurements. For this purpose, a coaxial electrode design was selected as the most suitable electrode design. Three tissue phantoms (blood, fat, muscle) were prepared from distilled water, sodium chloride, 1,2-propanediol, agar, and gelatine, and then characterized. Measurements were performed using an impedance analyzer in a range between 1 kHz and 1 MHz. A comparison with literature values showed good correspondance of the permittivity values determined, thus proving the applicability of the electrode design. However, the conductivity values measured were different from literature values. In the future, alteration and minimization of the electrode can be done to further improve the characterization.

Sensor-integrated needles with impedance or other electrochemical sensors have gained increased attention in research. Their potential use is widespread and covers applications such as early disease diagnostics or needle guidance for needle-based interventions. However, fabrication and sensor integration are crucial parts of realizing functionalized needles. In this paper, a review of existing research on microscale sensor arrays on curved needle surfaces is presented. It focusses on medical needles excluding needle-type sensors. Especially, means of fabrications including flexible thin-film-based sensors or photolithography are discussed. Although they provide satisfactory results, no manufacturing method is yet ready for bulk production.

Contactless blood pressure monitoring displays a chance for detecting hypertension and increasing the awareness of cardiovascular diseases. Camera-based methods show high potential for replacing inconvenient cuff-based technology. Blood pressure estimation through pulse transit time (PTT) and other parameters obtained from photoplethysmography (PPG) signal present a promising alternative to conventional blood pressure measurement. In this paper, recent approaches for contactless blood pressure monitoring were reviewed. All of the articles implemented systems based on PPG, whereas most of them used PTT as measuring parameter. The results are reviewed and summarized while pinpointing key challenges and discussing expectations for future research.

Localized impedance measurements at the needle tip identifying the present tissue type could aid clinicians in needle procedures. To assess the sensitivity field of a hollow, bipolar needle electrode, a 3D finite element approach using COMSOL Multiphysics was chosen. The simulated bipolar needle electrode consists of two hypodermic needles (17 G and 23 G) with an insulating layer of polytetrafluoroethylene (PTFE) in between. Impedance values were recorded while steadily increasing the insertion depth of the needle electrode in a layered tissue structure of skin (dermis), fat, and blood. Simulation results reveal a highly local sensitivity volume around the needle tip that can be approximated by half a tri-axial ellipsoid with elliptic radii of 0.735 mm, 2.886 mm, and 1.774 mm. A comparison with simulated and measured impedance values shows great correspondence.

Venepuncture is one of the most common invasive procedures performed worldwide, however, complications still occur. Currently, commercial single layer silicone phantoms used for venepuncture training do not accurately imitate the geometry and mechanical properties seen in the various patient groups. This paper presents the development of a realistic artificial venepuncture phantom. Three multilayered tissue phantoms are developed simulating venepuncture sites of paediatric, adult and geriatric patients. Silicone materials of different stiffnesses were selected to imitate the epidermis, dermis, subcutaneous fat, muscle and superficial veins. Singleaxis indentation tests were carried out on silicone samples and the multi-layered phantom inserts to characterize the material properties. The measured Young's moduli for the artificial dermis, fat and muscle show sufficient agreement with corresponding literature values. However, characterization of the complete phantom inserts showed stiffnesses four times larger than prior in-vivo studies. Future studies will work on developing a more comparable in-vivo study.

Many medical interventions in therapy and diagnostics require needle insertion into tissue. Common complications such as increased pain and formation of haematoma are caused by wrong needle positioning. It has been shown that pain experience and needle positioning can be improved by a reduction of insertion force, which can be achieved by vibrating the needle axially. An experimental setup has been designed to investigate the influences of different combinations of vibration frequencies (10, 100, and 200 Hz) and vibration amplitudes (20, 100, and 500 μm) during needle insertion into thin sheets of polyethylene terephthalate (PET). A customary 20 W loudspeaker was used to generate the vibration. The results indicate a maximum reduction of 73 % in puncture force and up to a 100 % reduction in shaft friction force. However, the additional vibration force generated by the vibration movement has to be high enough to generate positive effects in terms of force reduction.

The insertion of a needle into soft inhomogeneous tissue is required for many medical procedures. It has been shown that vibratory needle insertion methods have the ability to reduce insertion forces, which are correlated with increased needle placement precision, and reduced frequency and intensity of pain and trauma felt. This paper reviews different vibratory needle insertion methods that have been studied experimentally, addressing vibration generation, vibration frequency and amplitude, and force measurement. Reductions of up to 73 % in peak insertion force (150 Hz), and 37 % in placement error (15 Hz) were reported. Additionally, ultrasonic vibration (84 kHz) reduced the force by up to 28 %. The results of vibratory insertion show promise, specifically in regard to automated needle devices.

As an alternative to optical flow cytometry, magnetic flow cytometry has emerged in recent years for single cell analysis with sheath-less flow conditions. Instead of measuring scattered light, magnetic fields of magneticallylabeled cells are recorded and analyzed. To determine microfluidic opportunities to manipulate cell trajectories for in-situ cell focusing we use mechanical guiding structures and magnetophoretic forces. A 3D-microfluidic particle simulation has been implemented that revealed parameters ensuring the crucial balance between hydrodynamic drag and magnetophoretic forces. Experimental measurements verified the 3D particle tracking simulation.

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.ydbio.2009.07.029 Byline: Kazuki Hagihara (a), Eric E. Zhang (a)(b), Yue-Hai Ke (a), Guofa Liu (c), Jan-Jan Liu (a), Yi Rao (c), Gen-Sheng Feng (a)(b) Keywords: Signal transduction; Brain development; Neuronal cell migration Abstract: Shp2 is a non-receptor protein tyrosine phosphatase containing two Src homology 2 (SH2) domains that is implicated in intracellular signaling events controlling cell proliferation, differentiation and migration. To examine the role of Shp2 in brain development, we created mice with Shp2 selectively deleted in neural stem/progenitor cells. Homozygous mutant mice exhibited early postnatal lethality with defects in neural stem cell self-renewal and neuronal/glial cell fate specification. Here we report a critical role of Shp2 in guiding neuronal cell migration in the cerebellum. In homozygous mutants, we observed reduced and less foliated cerebellum, ectopic presence of external granule cells and mispositioned Purkinje cells, a phenotype very similar to that of mutant mice lacking either SDF-1[alpha] or CXCR4. Consistently, Shp2-deficient granule cells failed to migrate toward SDF-1[alpha] in an in vitro cell migration assay, and SDF-1[alpha] treatment triggered a robust induction of tyrosyl phosphorylation on Shp2. Together, these results suggest that although Shp2 is involved in multiple signaling events during brain development, a prominent role of the phosphatase is to mediate SDF-1[alpha]/CXCR4 signal in guiding cerebellar granule cell migration. Author Affiliation: (a) Burnham Institute for Medical Research, 10901 N. Torrey Pines Rd, La Jolla, CA 92037, USA (b) Molecular Pathology Graduate Program, University of California San Diego, La Jolla, CA 92093, USA (c) Department of Neurology, Northwestern University Feinberg School of Medicine, Chicago, IL 60611, USA Article History: Received 12 February 2009; Revised 7 July 2009; Accepted 20 July 2009

While many studies document that the market risk premium is predictable and that betas are not constant, the dividend discount model ignores time-varying risk premiums and betas. We develop a model to consistently value cashflows with changing risk-free rates, predictable risk premiums, and conditional betas in the context of a conditional CAPM. Practical valuation is accomplished with an analytic term structure of discount rates, with different discount rates applied to expected cashflows at different horizons. Using constant discount rates can produce large misvaluations, which, in portfolio data, are mostly driven at short horizons by market risk premiums and at long horizons by time variation in risk-free rates and factor loadings. [ABSTRACT FROM AUTHOR]

Background: Primary care physicians (PCPs) frequently have long-term relationships with patients as well as their families. As such they are well positioned to care for their patients at the end of their lives. As the number of patients in need of end-of-life care continues to grow, it is critical to understand how PCPs can fulfill that need. The purpose of our study is to perform a narrative review of the literature and develop a theoretical model delineating the overarching roles played by PCPs in caring for patients at the end of life. Methods: For this narrative review, the authors searched Medline (PubMed), Embase, Cochrane Library, and Scopus up to March 22, 2017. Articles were not limited by geography. Results: Review of existing literature generally supports 4 broad categories as the primary roles for PCP involvement in end of life: pain and symptom management; information management, including transmitting and clarifying information, setting care priorities, and assisting patients with treatment decisions; coordinating care and collaborating with other providers; and addressing patients' social, emotional, and spiritual needs. Conclusions: Based on the results of this review, PCPs provide a wide range of services to patients at the end of life. Promoting the provision of the full scope of services by PCPs will help ensure improved continuity of care while providing the highest quality of care for patients, both in the United States and around the world. [ABSTRACT FROM AUTHOR]