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Small Dimensions (small + dimension)
Selected AbstractsApplication of Krylov subspaces to SPECT imagingINTERNATIONAL JOURNAL OF IMAGING SYSTEMS AND TECHNOLOGY, Issue 5 2002P. Calvini The application of the conjugate gradient (CG) algorithm to the problem of data reconstruction in SPECT imaging indicates that most of the useful information is already contained in Krylov subspaces of small dimension, ranging from 9 (two-dimensional case) to 15 (three-dimensional case). On this basis, a new, proposed approach can be basically summarized as follows: construction of a basis spanning a Krylov subspace of suitable dimension and projection of the projector,backprojector matrix (a 106 × 106 matrix in the three-dimensional case) onto such a subspace. In this way, one is led to a problem of low dimensionality, for which regularized solutions can be easily and quickly obtained. The required SPECT activity map is expanded as a linear combination of the basis elements spanning the Krylov subspace and the regularization acts by modifying the coefficients of such an expansion. By means of a suitable graphical interface, the tuning of the regularization parameter(s) can be performed interactively on the basis of the visual inspection of one or some slices cut from a reconstruction. © 2003 Wiley Periodicals, Inc. Int J Imaging Syst Technol 12, 217,228, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ima.10026 [source] Intrahepatic cholangiocarcinoma diagnosed preoperatively as hepatocellular carcinomaJOURNAL OF SURGICAL ONCOLOGY, Issue 2 2004Masakazu Yamamoto MD Abstract Background Some cases of mass-forming intrahepatic cholangiocarcinoma (ICC) are diagnosed as hepatocellular carcinoma (HCC) based on preoperative imaging and clinical findings. We investigated the backgrounds of such cases. Methods Sixty-seven patients with mass-forming ICC underwent surgery from 1980 to 2002. Twenty-four of these patients received a diagnosis of HCC preoperatively. We compared the group diagnosed as HCC and that diagnosed as ICC. ICC was diagnosed histopathologically in all 67 patients. Results The specific clinical findings included high rates of associated hepatitis C virus infection, high levels of serum alpha fetoprotein, lower levels of serum CA19-9, small dimension of the tumor, hypervascular staining on angiography or computed tomography, lower rates of lymph node metastasis, and high rates of HCC occurrence in the group diagnosed as HCC. None of the patients underwent extrahepatic bile duct resection and most patients did not undergo lymph node dissection in the group diagnosed as HCC. The rates of mucus secretion and the ductal expression of mucin core protein-1 (MUC1) were significantly different between the subgroups. The cumulative survival rates were significantly better in the group diagnosed as HCC than in the group diagnosed as ICC. Conclusion Patients with ICC given a preoperative diagnosis of HCC had distinct clinical features and could be treated with the same operation as HCC patients. J. Surg. Oncol. 2004;87:80,83. © 2004 Wiley-Liss, Inc. [source] Multi-band chip antenna for WiMAX applicationsMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 6 2010Shun-Yun Lin Abstract A novel chip antenna for dual-/tri-band operation is presented in this article. The design consists of a pair of forked metal strips with different lengths. The longer strip is folded onto an FR4 base to simultaneously introduce the quarter- and half-wavelength modes as the first two operating bands. By varying the included angle between the sections of strip on the opposite base layers, the frequency ratio of the first two operating modes is adjusted over a large range of 1.34,2.29. In addition, the shorter excited strip introduces the quarter-wavelength mode as the third operating band. The tri-band operation with a small dimension of 13 × 5 × 0.8 mm3 for 2.5/3.5/5.5 GHz WiMAX applications is implemented. Experimental results show that the proposed antenna has good omnidirectional radiation patterns and steady antenna gains over all operating bands. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52: 1286,1290, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.25211 [source] A Contactless Impedance Probe for Simple and Rapid Determination of the Ratio of Liquids with Different Permittivities in Binary MixturesELECTROANALYSIS, Issue 1 2009Franti, ek Opekar Abstract Simple contactless cells with planar or tubular electrodes have been designed for measurement of the permittivity of solutions. The cells, connected to an integrated circuit of astable multivibrator, respond primarily to the capacitance component of the cell impedance, the multivibrator frequency depends in a defined manner on the solution permittivity and is readily used as the analytical signal in determinations of the ratios of components in binary liquid mixtures; water solution of methanol, ethanol and dioxane have been tested. The response of the cell with planar electrodes satisfies well the simple theoretical model and both the cells provide results with a sufficient sensitivity, a low LOD value (units of %vol) and a good precision (around 1%rel). The cell simplicity, small dimensions, long-term stability and the possibility of powering them from a battery make them suitable for hand-held meters. As an example of application in practice, the content of ethanol was determined in the car fuel petrol. [source] Automated diffusion chambers to monitor diurnal and seasonal dynamics of the soil CO2 concentration profileEUROPEAN JOURNAL OF SOIL SCIENCE, Issue 4 2009F. Albanito Summary To better understand the factors controlling carbon dioxide (CO2) production and transport in soil, we developed a new method to continuously monitor soil CO2 concentration at multiple depths, by using diffusion chambers. The soil diffusion chambers are constructed from a high-density polyethylene cylindrical frame enclosed by a micro-polyvinylidene difluoride flat membrane (PVDF). All chambers are linked to an infrared gas analyser positioned above-ground through a multi-port valve system. We set up two experimental sites for long-term measurements of soil CO2 concentration, soil temperature and soil water content at depths of 0, 10, 20, 40 and 80 cm. The system provides the following advantages : (i) the use of the PVDF combined with the small dimensions of the diffusion chambers allows rapid diffusion of soil gas into the chambers and therefore a short equilibration time of the gas phase with the surrounding soil atmosphere, (ii) the equilibrating closed loop system allows the semi-continuous measurement of soil profile CO2 concentrations without creating a pressure differential within the chambers, thus reducing gas concentration distortions in the soil, (iii) the small size of the closed diffusion chambers reduces the initial soil disturbance during installation, (iv) it allows sampling in wet, humid soils, including ones that are waterlogged or temporarily saturated, and (v) the chambers do not require removal for maintenance purposes and are inexpensive. [source] Gold Nanorods: From Synthesis and Properties to Biological and Biomedical ApplicationsADVANCED MATERIALS, Issue 48 2009Xiaohua Huang Abstract Noble metal nanoparticles are capable of confining resonant photons in such a manner as to induce coherent surface plasmon oscillation of their conduction band electrons, a phenomenon leading to two important properties. Firstly, the confinement of the photon to the nanoparticle's dimensions leads to a large increase in its electromagnetic field and consequently great enhancement of all the nanoparticle's radiative properties, such as absorption and scattering. Moreover, by confining the photon's wavelength to the nanoparticle's small dimensions, there exists enhanced imaging resolving powers, which extend well below the diffraction limit, a property of considerable importance in potential device applications. Secondly, the strongly absorbed light by the nanoparticles is followed by a rapid dephasing of the coherent electron motion in tandem with an equally rapid energy transfer to the lattice, a process integral to the technologically relevant photothermal properties of plasmonic nanoparticles. Of all the possible nanoparticle shapes, gold nanorods are especially intriguing as they offer strong plasmonic fields while exhibiting excellent tunability and biocompatibility. We begin this review of gold nanorods by summarizing their radiative and nonradiative properties. Their various synthetic methods are then outlined with an emphasis on the seed-mediated chemical growth. In particular, we describe nanorod spontaneous self-assembly, chemically driven assembly, and polymer-based alignment. The final section details current studies aimed at applications in the biological and biomedical fields. [source] Structural diversification of the gustatory organs during metamorphosis in the alpine newt Triturus alpestrisJOURNAL OF ANATOMY, Issue 3 2007Krystyna Abstract Gustatory organs of the taste bud type occur in the epithelial lining of the oropharyngeal cavity of alpine newt larvae. They resemble the taste buds of bony fish, both in appearance (as revealed by scanning electron microscopy) and in detailed internal structure (seen on transmission electron micropscopy). During metamorphosis, at stage 55 of development, the secondary tongue (i.e. the soft tongue) is well formed and the anlages of taste discs are clearly apparent. Somewhat later, taste discs also appear in the epithelial lining outside the tongue, paralleling the disappearance of the taste buds. Well-developed taste discs of the newt differ from taste buds mainly by their structurally diversified set of ,associate cells' (mucous, wing and glial cells), which have no synaptic contact with nerve fibres. These cells accompany the neurosensory cellular components of the taste disc, i.e. the taste receptor cells and basal cells. This indicates that gustatory organs in metamorphosed newts, regardless of their small dimensions, fulfil the criteria established for taste discs previously defined in other Caudata and Anura species. Therefore, in the development of the newt there are two subsequent types of gustatory organs and two generations of the tongue: primary, in the larvae, and secondary, in metamorphosed animals. [source] Synthesis and characterization of stimuli-sensitive micro- and nanohydrogels based on photocrosslinkable poly(dimethylaminoethyl methacrylate)JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 4 2007Smrati Gupta Abstract The aim of this work was the development of a versatile route for the preparation of temperature- and pH-responsive hydrogels with small dimensions. The copolymerization of N,N -dimethylaminoethyl methacrylate with various amounts (5 and 10 mol %) of dimethylmaleimidoethyl methacrylate in solution with 2,2,-azobisisobutyronitrile as an initiator is described. The structural and molecular characterization of the copolymers was performed with proton nuclear magnetic resonance, Fourier transform infrared, and ultraviolet spectroscopy, as well as size exclusion chromatography. Differential scanning calorimetry and thermogravimetry were used for the thermal characterization of the copolymers. Micro- and nanohydrogels of the copolymers were prepared by photocrosslinking. The gels obtained by photocrosslinking were characterized with a combination of surface plasmon resonance and optical waveguide spectroscopy, dynamic light scattering, and scanning electron microscopy. The hydrogels showed temperature- and pH-responsive behavior. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 669,679, 2007 [source] Microsurgical tracheotomy: A pediatric model in growing ratsMICROSURGERY, Issue 5 2003Mônica Cecília Bochetti Manna M.D. Previous studies described controversial opinions about pediatric tracheotomy concerning type of tracheal incision and long-term results, which remain as important research subjects. Experimental studies on rat tracheas are scarce, probably because of technical difficulties related to the structures' small dimensions. As many rat organ and system operative procedures were studied successfully by using microsurgical techniques, we decided to develop a pediatric tracheotomy model in growing rats which would permit long-term studies. Forty-four Wistar EPM-1 growing rats weighing 86 g and aged 35 days were divided into three groups: submitted to longitudinal, transverse, and segment excision of the trachea. Under sterile technique and intramuscular anesthesia (ketamine/xylazine), the trachea was exposed and incised, according to group, and a hand-made endotracheal cannula was inserted into the organ. This cannula was assembled using a segment of 1.5-cm-long 3 French silicone catheter passed through hexagonal-shaped silicone screen. The tracheal cannula was removed after 7 days, when we evaluated body weight, secretions, and dehiscence. In conclusion, this microsurgical tracheotomy model in growing rats is feasible, allowing studies on long-term repercussions of pediatric tracheotomy. © 2003 Wiley-Liss, Inc. MICROSURGERY 23:530,534 2003 [source] A dual-band split-ring monopole antenna for WLAN applicationsMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 11 2009Siddik Cumhur Basaran Abstract In this article, a novel dual-band microstrip monopole antenna based on split-ring elements is proposed for WLAN (2.4/5 GHz) applications. The antenna fed by a two-stage microstrip line has fairly small dimensions and provides 7.5 and 25.5% impedance bandwidth performance at the respective bands. Also, the antenna exhibits almost uniform radiation patterns at each frequency band. The measurement results of the fabricated antenna are in good agreement with the simulations. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 2685,2688, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24708 [source] 22 Comparison of multichannel electrogastrograms obtained with the use of three different electrode typesNEUROGASTROENTEROLOGY & MOTILITY, Issue 6 2006K JONDERKO Background/Aims:, Multichannel recording of the gastric myoelectrical activity (GMA) is a promising evolution of electrogastrography. In the study we searched for electrodes the most suitable to obtain high quality multi-channel electrogastrograms. Methods:, Twelve young volunteers (9 F, 3 M, aged 24.3 ± 0.6 years) underwent on separate days three four-channel electrogastrographic recordings of the GMA: 30 min fasted and 90 min after a solid meal stimulation. The electrogastrograms were recorded in randomized order with 3M Red Dot class Ag/AgCl electrodes designed primarily for long-term electrocardiographic monitoring: type2222 (conductive area, CA/total area, TA): 2.00/10.24 cm2, type2271 2.54/29.64 cm2, type2660 11.64/11.64 cm2 (total surface conductive!) and subsequently analysed with Polygram NetÔ EGG 311224 software (Medtronic, USA). Electrical resistance between active electrodes relative to the reference one was measured with a digital ohmmeter before and after the recording session. Results:, Type2660 yielded consistently higher electrical resistance than the other electrode types, moreover in the case of type2271 and type2660 electrical conductivity significantly improved at the end of the recording relative to the basal measurement. Analysis of variance involving the relative time-share of normogastria, meal-induced change in dominant power, as well as a set of parameters unique for the multichannel electrogastrography and intended to characterize the so-called spatial displacement of the gastric slow waves did not reveal any statistically significant effect of the electrode type on the parameters of the multichannel electrogastrogram. Although, when particular numerical data were inspected, type2271 was found to perform slightly worse than the other electrode types. Type2271 was also rated the less handy among the electrodes tested. Conclusion:, Multichannel surface electrogastrography seems to be technically feasible with any type of high quality Ag/AgCl electrodes available on the market, whereas small dimensions enabling easy placement on the abdomen may be a feature favouring the choice of a particular electrode type for this examination. [source] | |||||||||||||