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- 저자 : Berka, Vladimir (검색결과 4 건)
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Alhashash Mohamed,Zentralklinik Bad Berka, Bad Berka, Germany,Boehm Heinrich,Shousha Mootaz 대한척추외과학회 2022 Asian Spine Journal Vol.16 No.1
Study Design: This is a retrospective study with a minimum follow-up of 2 years.Purpose: The aim of this study is to assess the long-term outcomes after performing the four-level anterior cervical discectomy and fusion (ACDF) in the treatment of degenerative cervical spine disease using stand-alone titanium cages.Overview of Literature: Over the last decades, a rapid increase in the use of stand-alone cages for ACDF has been observed. However, research on their application in the treatment of four-level diseases is insufficient.Methods: In this study, 130 patients presenting with symptomatic cervical spondylosis who underwent four-level ACDF using standalone cages in our institution between 2008 and 2016 were assessed. Fifty-two patients were women and 78 men with a mean age of 60.5 years. Their clinical and radiological outcomes were assessed. The results of the Neck Disability Index (NDI) and Visual Analog Scale as well as bony fusion were evaluated, and the revisions were analyzed. All of the patients underwent the four-level microscopic ACDF using the same titanium rectangular cage.Results: The mean follow-up was 47±11.4 months. A fusion of all four levels was achieved in 80.72% of the patients. In 25 patients (19.23%), an incomplete bony bridging was observed in at least one fusion level at the final follow-up. However, only two patients (1.5%) were symptomatic and underwent revision. The mean NDI improved significantly from 39.4±9.3 at presentation to 8.3±6.6 at the final follow-up. Cervical lordosis improved significantly from a mean of 5.5° preoperatively to a mean of 15° postoperatively. Cage sinking and loss of segment height during healing had a mean of 3 mm.Conclusions: Overall, the application of four-level ACDF using titanium cages in a stand-alone technique has been proven to be a safe and effective treatment method for degenerative disease. In a large cohort, a high rate of good long-term clinical and radiological results was achieved.
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Kolá,ř,, Michal,Berka, Karel,Jureč,ka, Petr,Hobza, Pavel WILEY-VCH Verlag 2010 CHEMPHYSCHEM -WEINHEIM- Vol.11 No.11
<P>The reliability of the AMBER force field is tested by comparing the total interaction energy and dispersion energy with the reference data obtained at the density functional theory–symmetry-adapted perturbation treatment (DFT–SAPT)/aug-cc-pVDZ level. The comparison is made for 194 different geometries of noncovalent complexes (H-bonded, stacked, mixed, and dispersion-bound), at the equilibrium distances as well as at longer distances (up to a relative distance of two). The total interaction energies agree very well with the reference data and only the strength of H-bonded complexes is slightly underestimated. In the case of dispersion energy, the overall agreement is even better, with the exception of the stacked aromatic systems, where the empirical dispersion energy is overestimated. The use of AMBER interaction energy and AMBER dispersion energy for different types of noncovalent complexes at equilibrium as well as at longer distances is thus justified, except for a few cases, such as the water molecule, where the dispersion energy is highly inaccurate.</P> <B>Graphic Abstract</B> <P>The reliability of the AMBER force field is tested by comparing the total interaction energy and dispersion energy with the ab initio reference data. The comparison is made for 194 different geometries of noncovalent complexes with various binding motifs (see picture), at the equilibrium distances as well as at longer distances. Despite the oversimplified form of the empirical force field a surprisingly good agreement is observed, with some exceptions. <img src='wiley_img_2010/14394235-2010-11-11-CPHC201000109-content.gif' alt='wiley_img_2010/14394235-2010-11-11-CPHC201000109-content'> </P>
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Biodiesel flames as a unique pyrolyzing carbon source for the synthesis of hydrophobic carbon films
Duncan Merchan‑Breuer,Ethan Murphy,Benjamin Berka,Elena Echeverria,David N. McIlroy,Wilson Merchan‑Merchan 한국탄소학회 2021 Carbon Letters Vol.31 No.3
We report the rapid single-step flame synthesis of hydrophobic carbon layers (C-layers) on the surface of stainless-steel (SS) substrates using vaporized biodiesel as the fuel. A co-flow canola methyl ester/air diffusion flame is used to generate a hydrophobic monolayer on the surface of the metal substrate upon its insertion into the reaction zone. Carbon deposition on the surface of the SS substrates varies by changing the SS disk’s position in the post-flame, and by varying its exposure time. The thickness and mass of the flame-formed monolayer varied depending on the substrate’s insertion point into the flame. However, the variation of mass did not significantly impact the C-layer’s uniformity or hydrophobicity. We hypothesize that a small “inner-cone” of the biodiesel flame along with a high soot propensity can result in an ideal medium to form uniform hydrophobic C-layers of unique hierarchical surface structure. This is supported by introducing SS substrates in methane/air flames formed using the same co-flow burner. The hydrophobic property of the carbon deposits was quantified by measuring the contact angle of water droplets placed on the film’s surface. A water droplet drop test was conducted on the flame-formed hydrophobic layers to study their wettability property.
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Enhancement of the Electron Spin Resonance of Single-Walled Carbon Nanotubes by Oxygen Removal
Rice, William D.,Weber, Ralph T.,Leonard, Ashley D.,Tour, James M.,Nikolaev, Pavel,Arepalli, Sivaram,Berka, Vladimir,Tsai, Ah-Lim,Kono, Junichiro American Chemical Society 2012 ACS NANO Vol.6 No.3
<P>We have observed a nearly 4-fold increase in the electron spin resonance (ESR) signal from an ensemble of single-walled carbon nanotubes (SWCNTs) due to oxygen desorption. By performing temperature-dependent ESR spectroscopy both before and after thermal annealing, we found that the ESR in SWCNTs can be reversibly altered <I>via</I> the molecular oxygen content in the samples. Independent of the presence of adsorbed oxygen, a Curie law (spin susceptibility ∝ 1/<I>T</I>) is seen from ∼4 to 300 K, indicating that the probed spins are finite-level species. For both the pre-annealed and post-annealed sample conditions, the ESR line width decreased as the temperature was increased, a phenomenon we identify as motional narrowing. From the temperature dependence of the line width, we extracted an estimate of the intertube hopping energy; for both sample conditions, we found this hopping energy to be ∼1.2 meV. Since the spin hopping energy changes only slightly when oxygen is desorbed, we conclude that only the spin susceptibility, not spin transport, is affected by the presence of physisorbed molecular oxygen in SWCNT ensembles. Surprisingly, no line width change is observed when the amount of oxygen in the SWCNT sample is altered, contrary to other carbonaceous systems and certain 1D conducting polymers. We hypothesize that physisorbed molecular oxygen acts as an acceptor (p-type), compensating the donor-like (n-type) defects that are responsible for the ESR signal in bulk SWCNTs.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/ancac3/2012/ancac3.2012.6.issue-3/nn204094s/production/images/medium/nn-2011-04094s_0009.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/nn204094s'>ACS Electronic Supporting Info</A></P>
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