MedWorm: Physics Top 20

Complete electrode model in EEG: relationship and differences to the point electrode model.

Physics in Medicine and Biology — Sat, 04 Feb 2012 04:36:23 +0100

Authors: Pursiainen S, Lucka F, Wolters CH Abstract In electroencephalography (EEG) source analysis, a primary current density generated by the neural activity of the brain is reconstructed from external electrode voltage measurements. This paper focuses on accurate and effective simulations of EEG through the complete electrode model (CEM). The CEM allows for the incorporation of the electrode size, shape and effective contact impedance into the forward simulation. Both neural currents in the brain and shunting currents between the electrodes and the skin can affect the measured voltages in the CEM. The goal of this study was to investigate the CEM by comparing it with the point electrode model (PEM), which is the current standard electrode model for EEG. We used a three-dimension...

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On-line integration of computer controlled diagnostic devices and medical information systems in undergraduate medical physics education for physicians.

Physica Medica — Sat, 24 Dec 2011 05:00:00 +0100

Authors: Hanus J, Nosek T, Zahora J, Bezrouk A, Masin V Abstract We designed and evaluated an innovative computer-aided-learning environment based on the on-line integration of computer controlled medical diagnostic devices and a medical information system for use in the preclinical medical physics education of medical students. Our learning system simulates the actual clinical environment in a hospital or primary care unit. It uses a commercial medical information system for on-line storage and processing of clinical type data acquired during physics laboratory classes. Every student adopts two roles, the role of 'patient' and the role of 'physician'. As a 'physician' the student operates the medical devices to clinically assess 'patient' colleagues and records all results in an e...

Erratum: Conversion from unipolar to bipolar resistance switching by inserting TaO layer in Pt/TaO/Pt cells [Appl. Phys. Lett. 98, 183507 (2011)]

Applied Physics Letters — Sat, 04 Feb 2012 01:21:21 +0100

H. K. Yoo, S. B. Lee, J. S. Lee, S. H. Chang, M. J. Yoon et al. Abstract not available. [Appl. Phys. Lett. 100, 059901 (2012)] published Wed Feb 1, 2012. (Source: Applied Physics Letters)

Transformation kinetics of an intrinsic bistable defect in damaged silicon

Journal of Applied Physics — Tue, 31 Jan 2012 19:51:00 +0100

R. M. Fleming, C. H. Seager, D. V. Lang, and J. M. Campbell The positions of the electronic levels of an intrinsic bistable defect have been measured using deep level transient spectroscopy (DLTS) in n- and p-type damaged silicon bipolar transistor diodes after minority carrier injection and thermal annealing. The kinetic rates observed during conversion of ... [J. Appl. Phys. 111, 023715 (2012)] published Tue Jan 31, 2012. (Source: Journal of Applied Physics)

Amino acid analogues bind to carbon nanotube via pi-pi interactions: Comparison of molecular mechanical and quantum mechanical calculations

Journal of Chemical Physics — Mon, 16 Jan 2012 03:36:13 +0100

Zaixing Yang, Zhigang Wang, Xingling Tian, Peng Xiu, and Ruhong Zhou Understanding the interaction between carbon nanotubes (CNTs) and biomolecules is essential to the CNT-based nanotechnology and biotechnology. Some recent experiments have suggested that the pi-pi stacking interactions between protein's aromatic residues and CNTs might play a key role in their bindi ... [J. Chem. Phys. 136, 025103 (2012)] published Tue Jan 10, 2012. (Source: Journal of Chemical Physics)

A compartment‐specific transcriptome analysis reveals survival‐relevant marker genes in the stroma fraction of squamous non‐small cell lung cancer

Journal of Biophotonics — Sat, 28 Jan 2012 01:35:20 +0100

This study presents a compartment‐specific transcriptome analysis of lung squamous cell carcinoma (SCC) samples microdissected into tumor parenchyma and stroma fractions. Typical tumor and stroma genes were identified based on the expression ratios between the two compartments. Our results indicate that in SCC many markers related to longer survival are predominantly expressed in the stroma, particularly genes of the MHC‐II complex. Stromal upregulation of MHC‐II genes seems crucial for a clinically relevant antitumor immune response in SCC. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) (Source: Journal of Biophotonics)

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Improvement of temperature-stability in a quantum well laser with asymmetric barrier layers

Applied Physics Letters — Mon, 16 Jan 2012 03:35:18 +0100

Alexey E. Zhukov, Natalia V. Kryzhanovskaya, Fedor I. Zubov, Yuri M. Shernyakov, Mikhail V. Maximov et al. We fabricated and tested a quantum well laser with asymmetric barrier layers. Such a laser has been proposed earlier to suppress bipolar carrier population in the optical confinement layer and thus to improve temperature-stability of the threshold current. As compared to the conventional reference l ... [Appl. Phys. Lett. 100, 021107 (2012)] published Tue Jan 10, 2012. (Source: Applied Physics Letters)

Radiologist uses CT scans to replicate antique violin

Physics Today News Picks — Tue, 29 Nov 2011 05:00:00 +0100

BBC: A radiologist at the University of Minnesota is using computed tomography (CT) to replicate antique musical instruments. Steven Sirr first got the idea to take a CT scan of a violin in 1988. Such scans, he discovered, can reveal characteristics of the wood, worm holes and cracks, and previous repairs, all of which help create an instrument’s unique sound. Teaming up with a couple of violin makers, Sirr used more than 1000 CT images to reproduce a 1704 Stradivarius violin borrowed from the US Library of Congress. Over the years, the team has scanned hundreds of instruments, including guitars, mandolins, and other violins. "The copies are amazingly similar to originals in their sound quality," said Sirr, who hopes that the process will allow more music students to have access to h...

Dose to craniofacial region through portal imaging of pediatric brain tumors.

Journal of Applied Clinical Medical Physics — Tue, 17 Jan 2012 11:30:03 +0100

Authors: Hitchen CJ, Osa EO, Dewyngaert K, Chang J, Narayana A Abstract The purpose of this study was to determine dose to the planning target volume (PTV) and organs at risk (OARs) from portal imaging (PI) of the craniofacial region in pediatric brain tumor patients treated with intensity-modulated radiation therapy (IMRT). Twenty pediatric brain tumor patients were retrospectively studied. Each received portal imaging of treatment fields and orthogonal setup fields in the craniofacial region. The number of PI and monitor units used for PI were documented for each patient. Dose distributions and dose-volume histograms were generated to quantify the maximum, minimum, and mean dose to the PTV, and the mean dose to OARs through PI acquisition. The doses resulting from PI are reported...

Tracking of nanoscale structural variations on a single amyloid fibril with tip‐enhanced Raman scattering

Journal of Biophotonics — Wed, 25 Jan 2012 02:27:05 +0100

AbstractAmyloid fibrils are known to be responsible for diseases such as Alzheimer's disease. A detailed insight into the structure of amyloid fibrils is fundamental since it is not yet understood what triggers the misfolding of proteins to the fiber like structures. The molecular structure of fibril surfaces on a single amino acid level has not been revealed so far but would present a valuable contribution to this question. Here we demonstrate the direct molecular distinction of selected amino acids on insulin fibril surfaces with a lateral resolution better than 2 nm by applying tip‐enhanced Raman spectroscopy (TERS). This approach provides simultaneously a way to directly reveal conformational changes in the secondary structure, namely α‐helix, β‐sheet, on the fibril surface wit...

A three-dimensional model of an ultrasound contrast agent gas bubble and its mechanical effects on microvessels.

Physics in Medicine and Biology — Mon, 23 Jan 2012 08:30:28 +0100

In this study, the fluid shear and circumferential stresses were evaluated as indicators of the mechanical stresses. The effects of acoustical parameters, vessel viscoelasticity and rigidity, vessel/bubble size and off-centre bubbles on bubble behaviour and stresses on the vessel were investigated. The fluid shear and circumferential stresses acting on the vessel varied with time and location. As the frequency changed, the microbubble oscillated with the highest amplitude at its resonance frequency which was different from the resonance frequency of an unbound bubble. The bubble resonance frequency increased as the rigidity of a flexible vessel increased. The fluid shear and circumferential stresses peaked at frequencies above the bubble's resonance frequency. The more rigid the vessels we...

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A novel method for fast and robust estimation of fluorescence decay dynamics using constrained least-squares deconvolution with Laguerre expansion.

Physics in Medicine and Biology — Sat, 04 Feb 2012 04:38:31 +0100

We report a novel method for estimating fluorescence impulse response function (fIRF) from noise-corrupted time-domain fluorescence measurements of biological tissue. This method is based on the use of high-order Laguerre basis functions and a constrained least-squares approach that addresses the problem of overfitting due to increased model complexity. The new method was extensively evaluated on fluorescence data from simulation, fluorescent standard dyes, ex vivo tissue samples of atherosclerotic plaques and in vivo oral carcinoma. Current results demonstrate that this method allows for rapid and accurate deconvolution of multiple channel fluorescence decays without adaptively adjusting the Laguerre scale parameter. The appropriate choice of the scale parameter is essential for accurate ...

Atypical Neurofibroma and Osteosclerotic Metastasis

Journal of Biophysics — Mon, 16 Jan 2012 03:35:01 +0100

35-year-old male presented with multiple swellings in left leg, headache, weakness of limbs for 4 months, and blurring of vision for the last 15 days. On examination, he was pale, cachexic with generalized lymphadenopathy and lower motor neuron type weakness of limbs sparing right upper limb. Blood investigations showed anemia with high alkaline phosphatase. Chest radiograph revealed osteosclerotic metastatic lesion in humerus. Biopsy of leg lesion revealed atypical neurofibroma. Computed tomography (CT) of thorax revealed osteoblastic metastasis. Bone marrow aspiration showed cells with round to oval nuclei, fine granular chromatin with large central prominent nucleoli and eosinophilic cytoplasm with acini formation. Magnetic resonance imaging (MRI) of brain and spinal cord defined metast...

Reduced leakage current, enhanced ferroelectric and dielectric properties in (Ce,Fe)-codoped NaBiTiO film

Applied Physics Letters — Mon, 16 Jan 2012 03:35:18 +0100

C. H. Yang, G. D. Hu, W. B. Wu, H. T Wu, F. Yang et al. NaBiTiO (NBT), Ce-doped NBT (NBTCe), Fe-doped NBT (NBTFe), and (Ce,Fe)-codoped NBT (NBTCeFe) thin films were fabricated on LaNiO(100)/Si substrates by metal organic decomposition. The leakage current density of NBTCeFe at 500 kV/cm is reduced by approximately two orders of magnitude by reducing the ... [Appl. Phys. Lett. 100, 022909 (2012)] published Fri Jan 13, 2012. (Source: Applied Physics Letters)

Fourier transform infrared microspectroscopy identifies protein propionylation in histone deacetylase inhibitor treated glioma cells

Journal of Biophotonics — Sun, 22 Jan 2012 01:20:28 +0100

AbstractHistone deacetylase inhibitors (HDIs) have attracted considerable attention as potential drug molecules in tumour biology. In order to optimise chemotherapy, it is important to understand the mechanisms of regulation of histone deacetylase (HDAC) enzymes and modifications brought by various HDIs. In the present study, we have employed Fourier transform infrared microspectroscopy (FT‐IRMS) to evaluate modifications in cellular macromolecules subsequent to treatment with various HDIs. In addition to CH3 (methyl) stretching bands at 2872 and 2960 cm–1, which arises due to acetylation, we also found major changes in bands at 2851 and 2922 cm–1, which originates from stretching vibrations of CH2 (methylene) groups, in valproic acid treated cells. We further demonstrate that the ch...

Wolfgang von Ohnesorge

Physics of Fluids — Thu, 08 Dec 2011 14:35:58 +0100

Gareth H. McKinley and Michael Renardy This manuscript got started when one of us (G.H.M.) presented a lecture at the Institute of Mathematics and its Applications at the University of Minnesota. The presentation included a photograph of Rayleigh and made frequent mention of the Ohnesorge number. When the other of us (M.R.) enquired abou ... [Phys. Fluids 23, 127101 (2011)] published Wed Dec 7, 2011. (Source: Physics of Fluids)

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Optical planar waveguide for cell counting

Applied Physics Letters — Wed, 25 Jan 2012 02:28:03 +0100

In this report, we present a shallow, buried, planar waveguide fabricated by potassium ion exchange in glass that enables low-cost and rapid counting of metal-tagged objects ... [Appl. Phys. Lett. 100, 043701 (2012)] published Mon Jan 23, 2012. (Source: Applied Physics Letters)

Model of dissipative dielectric elastomers

Journal of Applied Physics — Sat, 04 Feb 2012 01:22:33 +0100

Choon Chiang Foo, Shengqiang Cai, Soo Jin Adrian Koh, Siegfried Bauer, and Zhigang Suo The dynamic performance of dielectric elastomer transducers and their capability of electromechanical energy conversion are affected by dissipative processes, such as viscoelasticity, dielectric relaxation, and current leakage. This paper describes a method to construct a model of dissipative dielec ... [J. Appl. Phys. 111, 034102 (2012)] published Fri Feb 3, 2012. (Source: Journal of Applied Physics)

Flu and climate may be connected

Physics Today News Picks — Wed, 18 Jan 2012 05:00:00 +0100

BBC: Global climate shifts and flu pandemics may be linked, say researchers. Weather can influence the migratory patterns of wild birds; thus different species are brought together that don’t normally mix. The birds then share viruses, which can morph into different strains to which the human population has not been previously exposed. In a paper published yesterday in the Proceedings of the National Academy of Sciences, Jeffrey Shaman of Columbia University and Marc Lipsitch of Harvard University note that the four most recent human influenza pandemics—in 1918, 1957, 1968, and 2009—were preceded by a climate pattern called La Niña. However, the researchers emphasize, most La Niñas have not preceded a pandemic. Rather, climate patterns could be one of several factors th...

Pharmacological Basis for the Medicinal Use of Lepidium sativum in Airways Disorders

Journal of Biophysics — Mon, 16 Jan 2012 03:35:01 +0100

Lepidium sativum is widely used in folk medicine for treatment of hyperactive airways disorders, such as asthma, bronchitis and cough. The crude extract of Lepidium sativum (Ls.Cr) inhibited carbachol (CCh, 1 μM-) and K+ (80 mM-) induced contractions in a pattern similar to that of dicyclomine. Ls.Cr at 0.03 mg/mL produced a rightward parallel shift of CCh curves, followed by nonparallel shift at higher concentration (0.1 mg/mL), suppressing maximum response, similar to that caused by dicyclomine. Pretreatment of tissues with Ls.Cr (0.1–0.3 mg/mL) shifted Ca++ concentration-response curves (CRCs) to right, as produced by verapamil. Ls.Cr at low concentrations (0.03–0.1 mg/mL) caused leftward shift of isoprenaline-induced inhibito...