Carbocations are crucial intermediates in many chemical reactions; hence, considerable effort has gone into investigating their structures and properties, for example, in superacids, in salts, or in ...the gas phase. However, studies of the vibrational structure of carbocations are not abundant, because their infrared spectra are difficult to obtain in superacids or salts (where furthermore the cations may be perturbed by counterions), and the generation of gas-phase carbocations in discharges usually produces several species. We have applied the technique of ionizing neutral compounds by X-irradiation of cryogenic Ar matrices to radicals embedded in such matrices, thus producing closed-shell cations that can be investigated leisurely, and in the absence of counterions or other perturbing effects, by various forms of spectroscopy. This Article describes the first set of results that were obtained by this approach, the IR spectra of the allyl and the benzyl cation. We use the information obtained in this way, together with previously obtained data, to assess the changes in chemical bonding between the allyl and benzyl radicals and cations, respectively.
Ruminacija je važan faktor kognitivne vulnerabilnosti za depresiju. Pored toga, ruminacija ima i transdijagnostički značaj u predviđanju različitih oblika psihopatoloških poremećaja, kao što su: ...anksiozni poremećaji, poremećaji ishrane, zloupotreba psihoaktivnih supstanci. Fenomen ruminacije najviše je izučavan u kontekstu depresije i smatra se značajnim kognitivnim faktorom vulnerabilnosti, koji predviđa nastanak, održavanje i ponovno javljanje depresivnih simptoma. Jedna od najšire prihvaćenih definicija ruminacije definiše ruminaciju kao skup ponašanja i misaonih obrazaca, koji dovode do pasivnog fokusa pažnje na depresivne simptome, implikacije i značenja tih simptoma. Fokusirajući se na simptome depresije (kao što su: potištenost, odsustvo motivacije, letargija, negativne misli i sl.), osoba nije u stanju da se fokusira na potencijalno adaptivne reakcije na negativna osećanja (kao što je na primer: anagažovanje u rešavanju problema), što posledično vodi održanju depresivnih simptoma, pojačavanju maladaptivnih obrazaca mišljenja o stresnim događajima, vlastitom selfu, budućem ponašanju. Brojne empirijske studije pokazale su da ruminacija kao odgovor na eksperimentalno indukovano ili prirodno nastalo depresivno raspoloženje dovodi do negativnih posledica, kao što su: pojačavanje i/ili perzistencija negativnog afekta i depresivnih simptoma, sklonost ka negativnom mišljenju, smanjena sposobnost rešavanja problema, snižena motivacija, inhibicija instrumentalnog ponašanja, narušena koncentracija i povećanje stresa.Osnovni ciljevi ovog istraživanju bili su empirijska provera internih metrijskih karakteristika i konstruktne valjanosti skale ruminativnog stila mišljenja i utvrđivanje njene prediktivne vrednosti u pogledu predviđanja perzistencije anksioznosti, depresivnosti i besa nakon eksperimentalnog zadatka ruminacije/distrakcije.Skala ruminativnog stila mišjenja je relativno nova skala, koja pretenduje da meri ruminaciju u širem kontekstu od depresivnog raspoloženja. Skala je operacionalizovana tako da meri dispoziciju ka repetitivnom mišljenju, koje je nezavisno od valence afekta, vremenske direkcije i sadržaja misli. Empirijska istraživanja autora skale pokazala su da ova skala ima veoma dobru prediktivnu vrednost u predviđanju depresivnih simptoma. Jedan od osnovnih ciljeva ovog istraživanja bio je da se utvrdi da li skala ruminativnog stila mišljenja zaista ima veću prediktivnu vrednost od do sada veoma korišćene i empirijski validirane skale ruminativnog stila reagovanja na depresiju i skala koje mere srodne konstrukte (brigu, anksioznost i depresivnost). Prediktivna vrednost skala ispitivana je u kontekstu tri vrste eksperimentalno indukovanog negativnog raspoloženja (tuge, anksioznosti i besa) nakon obavljenog eksperimentalnog zadataka ruminacije/distrakcije.Istraživanje je sprovedeno na uzorku od 180 ispitanika (150 devojaka i 30 momaka), uzrasta od 19 do 30 godina. Uzorak je prigodan i neujednačen po polu. Ispitanici su studenti prve, druge, treće i četvrte godine psihologije Filozofskog fakulteta, Univerziteta u Beogradu. Svi ispitanici su dali pisanu izjavu o informisanoj saglasnosti za učešće u istraživanju.Istraživanje se sastojalo iz dva dela. Prvi deo je bio korelaciona studija, a drugi deo eksperimentalna studija. U prvom delu istraživanja ispitivane su interne metrijske karakteristike i konstruktna validnost skale ruminativnog stila mišljenja. U svrhu provere divergentne i konvergente validnosti skale proveravane su relacije ove skale sa skalama koje mere depresivnu ruminaciju, brigu, simptome anksioznosti, depresivnosti i pet dimenzija bazične strukture ličnosti.U drugom delu istraživanja ispitivana je prediktivna vrednost skale ruminativnog stila mišljenja u kontekstu tri vrste eksperimentalno indukovanog negativnog raspoloženja (tuge, anksioznosti i besa).
Electronic portal imaging device (EPID) plays an important role in radiation therapy portal imaging, geometric and dosimetric verification. Consistent image quality and stable radiation response is ...necessary for proper utilization that requires routine quality assurance (QA). A commercial ‘EPID QC’ phantom weighing 3.8 kg with a dimension of 25×25×4.8 cm3 is used for EPID QA. This device has five essential tools to measure the geometric accuracy, signal‐to‐noise ratio (SNR), dose linearity, and the low‐ and the high‐contrast resolutions. It is aligned with beam divergence to measure the imaging and geometric parameters in both X and Y directions, and can be used as a baseline check for routine QA. The low‐contrast tool consists of a series of holes with various diameters and depths in an aluminum slab, very similar to the Las Vegas phantom. The high‐resolution contrast tool provides the modulation transfer function (MTF) in both the x‐ and y‐dimensions to measure the focal spot of linear accelerator that is important for imaging and small field dosimetry. The device is tested in different institutions with various amorphous silicon imagers including Elekta, Siemens and Varian units. Images of the QA phantom were acquired at 95.2 cm source‐skin‐distance (SSD) in the range 1–15 MU for a 26×26 cm2 field and phantom surface is set normal to the beam direction when gantry is at 0° and 90°. The epidSoft is a software program provided with the EPID QA phantom for analysis of the data. The preliminary results using the phantom on the tested EPID showed very good low‐contrast resolution and high resolution, and an MTF (0.5) in the range of 0.3–0.4 lp/mm. All imagers also exhibit satisfactory geometric accuracy, dose linearity and SNR, and are independent of MU and spatial orientations. The epidSoft maintains an image analysis record and provides a graph of the temporal variations in imaging parameters. In conclusion, this device is simple to use and provides testing on basic and advanced imaging parameters for daily QA on any imager used in clinical practices.
PACS number: 87.57 C‐, 87.57 N‐
Ultrasound-induced blood stasis has been observed for more than
30
years
. Most of the literature has been focused on the health risks associated with this phenomenon and methods employed to prevent ...stasis from occurring during ultrasound imaging. To date, experimental observations have been either in vitro or invasive. The current work demonstrates ultrasound-induced blood stasis in murine normal leg muscle versus tumor-bearing legs, observed through noninvasive measurements of optical spectroscopy, and discusses possible diagnostic uses for this previously undesirable effect of ultrasound. We demonstrate that, using optical spectroscopy, effects of ultrasound can be used to differentiate tumor from normal leg muscle tissue in mice. Finally, we propose a novel diagnostic algorithm that quantitatively differentiates tumor from nontumor with maximum specificity 0.83, maximum sensitivity 0.79, and area under receiver-operating-characteristics curve 0.90.
Robot-Assisted Prostate Brachytherapy Yu, Yan; Podder, Tarun; Zhang, Yongde ...
Medical Image Computing and Computer-Assisted Intervention – MICCAI 2006,
2006, Letnik:
9, Številka:
Pt 1
Book Chapter, Journal Article
Recenzirano
Odprti dostop
In contemporary brachytherapy procedures, needle placement at the desired target is challenging due to a variety of reasons. A robot-assisted brachytherapy system can improve the needle placement and ...seed delivery resulting in enhanced patient care. In this paper we present a 16 DOF (degrees-of-freedom) robotic system (9DOF positioning module and 7DOF surgery module) developed and fabricated for prostate brachytherapy. Techniques to reduce needle deflection and target movement have been incorporated after verifying with extensive experiments. Provisions for needle motion and force feedback have been included into the system for improving the robot control and seed delivery. Preliminary experimental results reveal that the prototype system is quite accurate (sub-millimeter) in placing brachytherapy needles.
To study the impact of seed localization, as performed by different observers using linked (125)I seeds, on postimplant dosimetry in prostate brachytherapy and, to compare transrectal ultrasound ...(TRUS)-based with CT-based approach for the dosimetric outcomes.
Nineteen permanent prostate implants were conducted using linked (125)I seeds. Postimplant TRUS and CT images were acquired and prostate glands were, after implantation, delineated on all images by a single oncologist, who had performed all 19 seeding procedures. Six observers independently localized the seeds on both TRUS and CT images, from which the principle dosimetric parameters V(100) (volume of prostate that received the prescribed dose), V(150) (volume of prostate that received 150% of the prescribed dose), and D(90) (minimal dose delivered to 90% of the prostate) were directly calculated for each patient. A single-factor analysis of variance was first applied to determine interobserver variability in seed localization. A nonparametric comparison of the approach using TRUS and CT was then carried out by the Wilcoxon paired-sample test.
Analysis from the analysis of variance for TRUS showed that the null hypothesis for equal means, could not be rejected for all six observers based on a significance level alpha=0.05. TRUS-based and CT-based approaches were then cross compared by the Wilcoxon paired-sample test, which suggested that the null hypothesis was insignificant for V(100) and D(90), but was significant for V(150).
Both TRUS- and CT-imaging modalities provided indistinguishable postimplant dosimetry results as far as V(100) and D(90) were concerned. There was comparable observer independence between TRUS- and CT-based seed localization for linked-seed implant procedures. With other advantages that TRUS-imaging modality had over CT in the evaluation of postimplant dosimetry, TRUS would be a preferred choice in conjunction with linked seeds for intraoperative procedures in prostate brachytherapy.
The Blake Archive is one of the most ambitious projects for digitizing a collection of illustrated works of William Blake. However, digitization of printed illustrations for archival purposes is not ...always a simple procedure. For example, colored engravings (a common book-illustration procedure of the 18th and 19th century) consist of regions of both very fine lines and almost uniformly colored regions. When trying to maintain a high compression rate for storage purposes, common compression algorithms cannot be applied. They tend to destroy fine lines (the high-frequency content) that are the essence of this type of image. In this thesis, an original modification of a Mixed Raster Content (MRC) compression scheme for the compression of colored engravings is presented. This modification produces a favorable compression result (compared to JPEG and JPEG2000) and, at the same time, provides numerous additional benefits to Blake scholars. These benefits include printing plate reconstruction, print comparisons, a separate study of the engraving and coloring process, and digital image enhancement. In order to modify the MRC imaging model for compression of the colored engravings, the image is first segmented in order to separate underlying lines and overlying coloring layers. The algorithms for image segmentation (i.e., line extraction) and for an approximation of the original etching print are developed. The coloring layer is then reconstructed using a novel data-filling algorithm. It is shown that image enhancement is possible via manipulation of this coloring layer prior to image reconstruction, and an algorithm for that enhancement is presented. The relationship between the original image and the image model is studied. Based on the physical image model, we are able to correct the paper aging effects and restore the original coloration. Finally, in our study of transmission strategies, we propose the use of the same channel for the transmission of both background (BG) and foreground (FG) layers. The mask layer is used at extremely low bit rates to emphasize lines, but the model gradually changes toward standard JPEG2000 as the download progresses. In this way, we combine the MRC approach and efficiency of the JPEG2000 coding to improve the image quality (at low bit ratios) and to simplify data management on the server side.
PDF
