Polymer translocation induced by adsorption

We study the translocation of a flexible polymer through a pore in a membrane induced by its adsorption on \trans side of the membrane. When temperature $T$ is higher than $T_c$, the adsorption-desorption transition temperature, attractive interaction between polymer and membrane plays little role in affecting polymer conformation, leading to translocation time that scales as $\tau\sim L^3$ where $L$ is the polymer contour length. When $T < T_c$, however, the translocation time undergoes a sharp crossover to $\tau\sim L^2$ for sufficiently long polymers, following the second order conformational (adsorption) transition. The translocation time is found to exhibit the crossover around $T=T_c'$, which is lower than $T_c$ for polymers shorter than a critical length($N<N_c$).Comment: 19 pages RevTeX, 5 postscript figures, to be published in J. Chem. Phys. 108(7), 3013 (1998

Polymer Release out of a Spherical Vesicle through a Pore

Translocation of a polymer out of curved surface or membrane is studied via mean first passage time approach. Membrane curvature gives rise to a constraint on polymer conformation, which effectively drives the polymer to the outside of membrane where the available volume of polymer conformational fluctuation is larger. Considering a polymer release out of spherical vesicle, polymer translocation time $\tau$ is changed to the scaling behavior $\tau\sim L^2$ for $R<R_G$, from $\tau\sim L^3$ for $R\gg R_G$, where $L$ is the polymer contour length and $R$, $R_G$ are vesicle radius and polymer radius of gyration respectively. Also the polymer capture into a spherical budd is studied and possible apparatus for easy capture is suggested.Comment: 14 pages RevTeX, 6 postscript figures, published in Phys. Rev. E 57, 730 (1998

Penetrating Carotid Artery Injuries Treated by an Urgent Endovascular Stent Technique: Report of Two Cases

Penetrating neck injuries are potentially dangerous and require emergent management because of the presence of vital structures in the neck. Penetrating vascular trauma to zone I and III of the neck is potentially life-threatening. An accurate diagnosis and adequate surgical intervention are critical to the successful outcome of penetrating trauma in the neck. We experienced some cases with externally penetrating injuries in neck zone II in which the patients were confirmed to have the presence of large vessel injuries in neck zones I and III. Here we report on the endovascular stent techniques used in two cases to address penetrating carotid artery injuries and review the literature

Metastatic Gastric Adenocarcinoma Presenting as a Solitary Plaque on the Palm

Cutaneous metastases from gastric adenocarcinoma are extremely rare. When present, metastasis typically signifies disseminated disease with a poor prognosis. We report a case of an 80-year-old male with gastric cancer who presented with a single, erythematous plaque on the left palm, a very rare site for skin metastasis. Results of a skin biopsy demonstrated that the cutaneous metastasis originated from the stomach. This report emphasized the need for appropriate investigation into newly appearing, unusual, or persistent skin lesions

Statistical Mechanics of Membrane Protein Conformation: A Homopolymer Model

The conformation and the phase diagram of a membrane protein are investigated via grand canonical ensemble approach using a homopolymer model. We discuss the nature and pathway of $\alpha$-helix integration into the membrane that results depending upon membrane permeability and polymer adsorptivity. For a membrane with the permeability larger than a critical value, the integration becomes the second order transition that occurs at the same temperature as that of the adsorption transition. For a nonadsorbing membrane, the integration is of the first order due to the aggregation of $\alpha$-helices.Comment: RevTeX with 5 postscript figure

Outbreak investigation of Serratia marcescens neurosurgical site infections associated with a contaminated shaving razors

Abstract Background Surgical site infection (SSI) is the most common healthcare-associated infection. We report an outbreak of neurosurgical site infections caused by Serratia marcescens after craniotomy in a tertiary care hospital. Methods Between August 6 and 21, 2018, five cases of early-onset SSI caused by S. marcescens after craniotomy were recorded in a 1786-bed tertiary care hospital. Cultures were collected from potential environmental sources and healthcare workers. Whole-genome sequencing (WGS) was used to investigate the genetic relationships among S. marcescens isolates. Results The outbreak involved five patients; S. marcescens was isolated from the cerebrospinal fluid, pus, tissue, and blood samples from these patients. S. marcescens was also isolated from shaving razors and brushes. All S. marcescens isolates from the infected patients and razors showed the same resistance patterns on antibiotic-susceptibility tests. WGS revealed close clustering among four of five isolates from the patients and among three of four isolates from the razors. No additional patient developed S. marcescens infection after we stopped using the razors for scalp shaving. Conclusions We report an outbreak of neurosurgical site infections after craniotomy, which was associated with shaving razors contaminated by S. marcescens. Shaving scalps with razors should be avoided to prevent SSI

Design and Implementation of High Switching Frequency LLC Resonant Converter for High Power Density

A design methodology of a dual active bridge (DAB) converter for solid state transformer applications is proposed using an elaborate mathematical model of the converter. The DAB converter is popular in bi-directional power conversion applications because of soft switching capability and seamless control in bi-directional power flows. However, several design considerations should be considered to overcome its demerits such as high RMS current at heavy load condition and limited soft switching capability at light load condition. Design methodology of the power stage will be discussed to minimize the conduction loss and to enlarge the soft switching region. In addition, the algorithm for soft start will be discussed to reduce overcurrent stress of the power switches during a start-up sequence. Experimental results of a 3.3 kW prototype DAB converter demonstrate the validity and effectiveness of the proposed methods

TiO2 Decorated Low-Molecular Chitosan a Microsized Adsorbent for a 68Ge/68Ga Generator System

We report column material for a 68Ge/68Ga generator with acid resistance and excellent adsorption and desorption capacity of 68Ge and 68Ga, respectively. Despite being a core element of the 68Ge/68Ga generator system, research on this has been insufficient. Therefore, we synthesized a low molecular chitosan-based TiO2 (LC-TiO2) adsorbent via a physical trapping method as a durable 68Ge/68Ga generator column material. The adsorption/desorption studies exhibited a higher separation factor of 68Ge/68Ga in the concentration range of HCl examined (0.01 M to 1.0 M). The prepared LC-TiO2 adsorbent showed acid resistance capabilities with &gt;93% of 68Ga elution yield and 1.6 × 10−4% of 68Ge breakthrough. In particular, the labeling efficiency of DOTA and NOTA, by using the generator eluted 68Ga, was quite encouraging and confirmed to be 99.65 and 99.69%, respectively. Accordingly, the resulting behavior of LC-TiO2 towards 68Ge/68Ga adsorption/desorption capacity and stability with aqueous HCl exhibited a high potential for ion-exchange solid-phase extraction for the 68Ge/68Ga generator column material

A study on plastic deformation resistance test between glass fiber reinforced asphalt and modified SMA mixture

In recent years, modified SMA (Stone Mastic Asphalt) mixtures, which exhibit high performance in terms of plastic deformation and crack resistance, have been widely used in Korea. However, the modified SMA mixture is difficult to supply and receive aggregate, and has a problem that it costs more than a normal hot-mix asphalt mixture.   Recently, glass fiber reinforced asphalt mixtures have been developed as an alternative to the modified SMA blend. In this study, the plastic deformation resistance of the glass fiber reinforced asphalt mixture and the modified SMA mixture was evaluated by Hamburg Wheel Tracking and APT (Accelerated Pavement Testing). It has its purpose. The modified SMA used in the experiment was a mixture of a PG76-22 binder commonly used in Korea and a maximum particle diameter of 13 mm. The glass fiber reinforced asphalt mixture was analyzed for air void and Marshall stability according to the amount of fiber added to the mixture of normal hot-mix asphalt mixture using WC-2 particle size and PG64-22 binder commonly used in Korea and the optimum fiber amount was deduced. Three kinds of fiber addition were selected as 0.25%, 0.5% and 1.0%, and three marshall specimens were prepared for each case to analyze porosity and Marshall stability. As a result of regression analysis, it was shown that the maximum Marshall stability was satisfied in the range of satisfying the porosity criterion when 0.6% of fiber was added.  For each of the above mixtures, a Hamburg wheel tracking specimen with air void of 7% was fabricated using a gyrotary compaction machine. In the Hamburg wheel tracking test, 20,000 loadings were applied under the condition that each mixture specimen was immersed in water at 50 ℃, and the Permanent Deformation of each mixture specimen was measured by LVDT (Linear Variable Differential Transformer). The results of the Hamburg wheel tracking test are shown in Figure

Tumor Targeting Effect of Triphenylphosphonium Cations and Folic Acid Coated with Zr-89-Labeled Silica Nanoparticles

In this study, we investigated the tumor targeting effect in cancer cells using triphenylphosphonium (TPP) cations, which are accumulated by differences in membrane potential, and folic acid (FA), which is selectively bound to overexpressed receptors on various cancer cells. We used Food and Drug Administration (FDA)-approved silica nanoparticles (SNPs) as drug carriers, and SNPs conjugated with TPP and FA (STFs) samples were prepared by introducing different amounts of TPP and FA onto the nanoparticle surfaces. STF-1, 2, 3, 4 and 5 are named according to the combination ratio of TPP and FA on the particle surface. To confirm the tumor targeting effect, 89Zr (t1/2 = 3.3 days) was coordinated directly to the silanol group of SNP surfaces without chelators. It was shown that the radiochemical yield was 69% and radiochemical purity was &gt;99%. In the cellular uptake evaluation, SNPs with the most TPP (SFT-5) and FA (SFT-1) attached indicated similar uptake tendencies for mouse colon cancer cells (CT-26). However, the results of the cell internalization assay and measurement of positron emission tomography (PET) images showed that SFT-5 had more affinity for the CT-26 tumor than other samples the TPP ratio of which was lower. Consequently, we confirmed that TPP ligands affect target cancer cells more than FA, which means that cell membrane potential is significantly effective for tumor targeting