Slit Dimensions Research Articles

Modeling Transmigration of Malaria Infected Red Blood Cells through Inter-Endothelial Slits in Human Spleens using Dissipative Particle Dynamics

We simulate the transmigration of malaria-infected red blood cells (RBCs) through the inter-endothelial slits in the human spleen by using Dissipative Particle Dynamics based two-component RBC model. We modeled the spectrin-actin network and the lipid bilayer separately and considered the real number of the structural proteins in the model. The mechanical properties of the bilayer-cytoskeletal interactions, such as stiffness and friction, are calibrated by comparing with membrane fluctuations and tank-treading experiments. First, we further validated our numerical model by comparing the predicted retention rates of healthy and pathological cells in an ‘artificial spleen’ consisting of micro beads with the experimental measurements. To explore the possibility of the bilayer-cytoskeletal detachment during this transmigration process, which is strongly related to RBC aging and hereditary spherocytosis, we predicted the maximum interaction force between the spectrin-actin cytoskeleton and the lipid bilayer and compared the value with the previously predicted bilayer-cytoskeletal bond strength. Furthermore, we systematically studied the effects of cell rigidity, cell shape and inter-endothelial slit dimensions on the critical pressure gradient for RBCs to pass through the spleen. We found that the cell shape plays a much more important role than the cell rigidity in the transmigration process, which may guide the future experiments and the drug design for eradicating malaria and treating anemia such as hereditary spherocytosis.

Note: Compact, two-dimension translatable slit aperture

A compact, light-weight, two-dimension translatable slit aperture is described. The slit dimensions are scalable, allowing for wide application. With all metal construction, the device would be suitable for high temperature degassing and vacuum compatible. Alternatively, the main structure may be printed using a 3D printer for rapid prototyping and/or lighter weight. The precision of the slit movement is 0.014 mm.

Enhanced resonant transmission of electromagnetic radiation through a pair of subwavelength slits

We show that a pair of subwavelength slits in parallel conducting plates supports a localized electromagnetic mode bound to the slits, whose spatial extent is determined not by the plates' size but by the slit dimensions. This mode occurs for electric fields parallel to the slits and plate separation slightly smaller than half the free-space wavelength. Finite element calculations and experimental results at 10 GHz show that the localized mode gives rise to a strong, narrowband resonant enhancement of the transmission which, while limited by conduction losses in the plates, is a factor of 104 larger than for off-resonant transmission.

Electronically tunable aperiodic distributed feedback terahertz lasers

Focussed ion beam milling can be used to introduce aperiodic distributed feedback (ADFB) gratings into fully packaged, operational terahertz (THZ) quantum cascade lasers to achieve electronically controlled, discretely tunable laser emission. These aperiodic gratings—designed using computer-generated hologram techniques—consist of multiple slits in the surface plasmon waveguide, distributed along the length of the laser cavity. Tuning behaviour and output power in ADFB lasers operating around 2.9 THz are investigated with a variety of slit dimensions and grating scales. Mode selectivity and grating losses are found to be strongly dependent on milling depth into the upper waveguide layers, dramatically increasing as the metallic layers are penetrated, then rising more slowly with deeper milling into the laser active region. Grating scale and placement along the laser cavity length are also shown to influence mode selection.

Characteristics of integrated micro packed bed reactor-heat exchanger configurations in the direct synthesis of dimethyl ether

The performance of three integrated micro packed bed reactor-heat exchangers (IMPBRHEs) for direct DME synthesis over physical mixtures of CuO–ZnO–Al2O3 and γ-Al2O3 catalysts was experimentally investigated. Systematic variations in reactor and slit dimensions and configuration were analyzed in terms of thermal behaviour, mass transfer, pressure drop and residence time distribution (RTD). The pressure drop was always small (<0.12bar) relative to the total pressure (50bar), and linear dependence with GHSV confirms the predicted laminar flow for Re=0.1–2. A narrow RTD was estimated by the dispersion analysis. Careful temperature measurements confirmed that the reaction temperature is mainly controlled by the oil heat exchange to give a practically uniform temperature profile for set inlet oil temperatures of 220–320°C. The micro packed beds were found free of the internal as well as external mass transfer limitations, as showed by no significant change in the CO conversion and DME yield for different catalyst particle sizes, no effect of varying the linear gas velocity, and no effect of manipulating reactant diffusion coefficient. Packed bed microstructured reactors hence provide an isobaric and isothermal environment free from transport limitations for the direct DME synthesis, in the kinetic regime as well as at equilibrium conversion.

Studying Systematic Errors on Estimation Decision, Detection, and Quantification Limit on Micro-TLC

The decision limit (CCα), capability of detection (CCβ) and quantification limit (QL) are importance performance characteristics in method validation. The TLC-Scanner 3 from Camag provides the possibility to choose the slit dimension of light to determine the peak chromatogram of a substance. The influence of the slit dimension for determination of CCα, CCβ and QL of paracetamol has been carried out. Paracetamol was spotted onto plates of AL-TLC Si G 60 F254 by linomat 4 in the range of 50–400 ng/spot and 10–400 ng/band, then on twin chambers eluted with TAEA (toluene:acetone-ethanol:conc.ammonia, 45 + 45 + 7 + 3 v/v) for 45 mm. Eluted spots were scanned in different slit dimensions at 248 nm. The CCα, CCβ and QL of paracetamol were estimated through the linear regression (LRM) and signal-to-noise (S/N) methods. Slit lengths between 50 and 133 % of the band width of the spots, and with the noise factor of the slit under 2.6, produced good precision measurements of TLC-densitometry between plates, while slit lengths between 50 and 83 % of the band width of the spots introduced a higher sensitivity response of the detector. The estimated CCα, CCβ and QL were determined by how the data were collected, the analytical optical setting, and the usage method for the estimation of both validation parameters.

Modal-based prediction of sound transmission through slits and openings between rooms

The transmission of sound through slits and openings between cuboid-shaped rooms is analysed. A deterministic model that describes the pressure fields inside the rooms in terms of eigenfunctions and uses the Dirichlet-to-Neumann technique in order to reproduce the slit effect is presented. An efficient formulation of the problem is obtained thanks to the splitting of the original domain into three domains: sending room, slit, receiving room. The geometry and boundary conditions of the problem can be modelled in detail like in an element-based numerical technique (such as the finite element method) but with smaller computational costs. The model is compared with numerical solutions, existent models and published experimental data. Afterwards it is used to analyse some aspects such as the influence of slit dimensions, opening position, room properties (dimensions and absorption) that cannot be taken into account with the available models. These usually suppose that the slit or opening connects two unbounded acoustic domains.

A multiobjective optimization of a UWB antenna using a self organizing genetic algorithm

AbstractThis article presents the optimization process of a microstrip antenna designed to operate with ultra‐wideband applications. This optimization process was accomplished by applying a self organizing multiobjective genetic algorithm (GA) to optimize a geometry aspect of a ring monopole antenna (a slit in the ground plane) considering three objectives simultaneously (bandwidth, return loss and central frequency deviation). Each of these objectives are modeled as dependent of two variables (the slit dimensions) and used in a single weighted compound aggregate objective function in which weights are defined by an adjuster GA that uses another GA to evaluate each combination of possible weights. The results were compared with the ones obtained to the same antenna using a simulator program (Ansoft HFSS) and with the results of a real prototype antenna built from the slit dimension optimal values obtained after the optimization process. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 54:1824–1828, 2012; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26945

High-throughput and multislit imaging spectrograph for extended sources

We describe a high-throughput (5×10 -4 cm 2 sr) imaging spectrograph that uses an echelle grating operating at a high dispersion order (24 to 43) to observe extended sources such as atmospheric airglow and diffuse proton aurora at high spectral resolution (approximately 0.02 nm). Instead of using a traditional single slit, the implementation of the instrument described here uses four (50 µm × 25 mm) slits through which the radiation enters the spectrograph. The field of view is selected using appropriate foreoptics: the present implementation is a long, narrow configuration of 0.1 × 50 deg. By placing interference filters in the beam path, the instrument can simultaneously observe several spectral features located anywhere in the visible band (approximately 300 to 1000 nm) at high resolution. This design allows a single echelle grating and a single detector (a CCD in the present implementation) to view the same scene. The design is flexible; the number of slits and the slit dimensions can be tailored to the trade-offs between resolution, throughput, and number of spectral features depending upon the measurement need. While the implementation described here covers only the visible range, the use of different combinations of detector and filter sets can extend its operation to other wavelength regions.

Field-Dependent DNA Mobility in 20 nm High Nanoslits

The transport behavior of lambda-DNA (48 kbp) in fused silica nanoslits is investigated upon application of electrical fields of different strengths. The slit dimensions are 20 nm in height, 3 microm in width, and 500 microm in length. With fields of 30 kV/m or below, the molecules move fluently through the slits, while at higher electrical fields, the DNA molecules move intermittently, resulting in a strongly reduced mobility. We propose that the behavior can be explained by mechanical and/or field-induced dielectrophoretic DNA trapping due to the surface roughness in the nanoslits. The observation of preferential pathways and trapping sites of the lambda-DNA molecules through the nanoslits supports this hypothesis and indicates that the classical viscous friction models to explain the DNA movement in nanoslits needs to be modified to include these effects. Preliminary experiments with the smaller XbaI-digested litmus-DNA (2.8 kbp) show that the behavior is size-dependent, suggesting that the high field electrophoresis in nanoslits can be used for DNA separation.

A complex parameter boundary element method for modeling AC impedances of electrochemical systems by analytic continuation—Application to a slit geometry

A complex parameter boundary element method is advanced to compute the AC impedances of electrochemical systems by solving the Laplace equation with complex boundary conditions. This method, which is based on analytic continuation from the corresponding secondary current distribution, is applied to a slit geometry, besides two illustrative cases: plane-parallel electrodes and concentric cylinder electrodes. The AC impedance responses for the slit geometry are computed for several electrode and slit dimensions for (1) purely capacitive working electrode and (2) a working electrode represented by a Voigt element. Interesting effects of the electrode and the slit dimensions on the AC response are noted. Applications of this method in viscoelastic systems, rheology and electronic/electrical devices are discussed. User-friendly implementations of the method in the BEASY group of softwares are also suggested.

A monolithic Fresnel bimirror for hard X-rays and its application for coherence measurements

Experiments using a simple X-ray interferometer to measure the degree of spatial coherence of hard X-rays are reported. A monolithic Fresnel bimirror is used at small incidence angles to investigate synchrotron radiation in the energy interval 5-50 keV with monochromatic and white beam. The experimental set-up was equivalent to a Young's double-slit experiment for hard X-rays with slit dimensions in the micrometre range. From the high-contrast interference pattern the degree of coherence was determined.

Observations of Mercury's exosphere: Spatial distributions and variations of its Na component during August 8, 9 and 10, 2003

Following the observations of August 2002 [Barbieri, C., Verani, S., Cremonese, G., Sprague, A., Mendillo, M., Cosentino, R., Hunten, D., 2004. Planet. Space Sci. 52, 1169–1175], the high resolution spectrograph of the 3.5-m Galileo National Telescope (TNG) has been used to obtain several spatially resolved spectra of Mercury's Na-D on the evenings of 8, 9 and 10 August 2003. The resolution of the spectrograph was 115,000, the slit dimensions were 0.4 ″ × 27 ″ . With respect to Paper I, the planet was in a fairly similar orbital configuration, being at a geocentric distance of approximately 1 AU, and having a True Anomaly Angle (TAA) from 163°–168° instead of 171°–174°. We present here a significantly larger set of observations and discuss several important features regarding the formation of Mercury's sodium exosphere, in particular the role of photon stimulated and thermal desorptions, as well as of the solar wind sputtering and micro-meteoroid vaporization. Thanks to the very good seeing of these observations, we also report and discuss the origins and variations of equatorial structures in Mercury's early morning sodium exosphere.

Ultrastructural comparison of Aplysia and Dolabrifera ink glands suggests cellular sites of anti-predator protein production and algal pigment processing

Ultrastructural comparison between the ink gland of a sea hare species that produces copious purple ink (Aplysia californica) and one that produces none (Dolabrifera dolabrifera), suggests that the rough endoplasmic reticulum rich cell and not the ink vesicle cell is the site for synthesis of A. californica's anti-predator ink protein, escapin. Dolabrifera dolabrifera were found to have vestigial ink glands incapable of producing ink or its associated anti-predator proteins regardless of diet. This study also suggests that the granulate cells serve only as a storage site for excess ink pigment acquired during periods of luxury feeding on red algae. Slit dimensions in sieve areas of granulate cells are also significantly different between the two species. These slit sizes are larger than those of rhogocytes, a related cell type commonly found in connective tissue of gastropod molluscs. Several traits of granulate cells suggest that they are distinct from rhogocytes and are a special cell type in the ink gland of sea hares.

Electrophoresis of a bead-rod chain through a narrow slit: A Brownian dynamics study

We use two-dimensional Brownian dynamics simulations to study the electrophoresis of a bead-rod chain through a narrow slit. A constant electric field is assumed to act inside and outside of the slit, and each bead on the chain is assigned a constant uniform charge. We calculate the dependence of the polymer transit velocity on chain length, slit dimensions (width-to-length ratio), and electric-field strength. For sufficiently narrow slits, the transit velocity increases nonlinearly with the applied field for low-field strengths, whereas it increases linearly for high-field strengths. In the low-field strength region and for sufficiently narrow slits, the transit velocity decreases rapidly for small chain lengths and then decreases slowly beyond a critical chain length. As the slit width increases, the transit velocity decreases with chain length in more continuous manner, and for sufficiently large slits the transit velocity becomes independent of chain length as expected. Distributions of the chain end-to-end distances and the translocation times depend strongly on the relative size of the chain to the slit. These results show the sensitivity of the transit velocity vs chain length relationship to the slit dimensions and applied electric-field strength, and suggest that there may be an optimal slit width for a given field strength and vice versa. The results may be useful for microfluidic separations and for understanding the motion of biological polymers through narrow constrictions.

Photolithographic fabrication of diffraction and interference slit patterns for the undergraduate laboratory

Measuring the interference and diffraction patterns produced by light passing through single and double narrow slits is a classic undergraduate physics experiment that dramatically confirms the wave nature of light. Despite this critical educational role, the experiment often is problematic because of the failings of commercially available slit patterns which produce faint unconvincing projected patterns. We discuss a low cost photolithographic process that produces diffraction slits in a chromium film deposited on a glass substrate. Slit dimensions as small as 4 μm are attainable with this method with complete control over the spacing of double slits. The method also can be used to expand the variety of slit patterns to two-dimensional arrays and circular patterns.

Optimum collimator shape and maximum emittance for submicron focusing of ion beams. Determination of the probe-forming system resolution limit

Improvements in the spatial resolution of instrumentation using focused ion beams are connected with further reduction of the beam spot size, while the beam intensity is kept sufficiently high. In search for probe-forming systems (PFS) of new generation it is important to determine the lower theoretical resolution limit for each system. In this case the lower resolution limit can be taken to be quality-factor of the system. As a general approach permitting the resolution limit to be found the authors propose the method of the maximum beam emittance. By proper selection of the object and angular slit dimensions and their positions with respect to the axis of the PFS, one attains the maximum beam emittance for a prescribed beam spot size. Calculations involving only demagnification and aberration coefficients allow a comparison to be made between different PFS irrespective of their dimensions and focusing elements employed. Investigations into conventional magnetic quadrupole PFS show that parasitic sextupole field components present in the lenses can lead to the asymmetric position of the angular slit and thus, to asymmetric position of the beam along the optical line.

Microstrip-fed dual-frequency printed triangular monopole

A new, compact, microstrip-fed printed equilateral triangular monopole with dual-frequency operation is described. Various frequency ratios, within the range 1.37–1.75, of the two operating frequencies can be obtained by varying the trapezoidal slit dimensions of the triangular patch. Omnidirectional radiation patterns of the two operating frequencies are given for the proposed antenna.

Optimization of magnetic quadrupole probe forming systems based on separated Russian quadruplet

This paper describes computer simulation of the optimum lens arrangement and collimator slit dimensions in magnetic quadrupole probe forming systems based on separated Russian quadruplet with a view to attain the maximum emittance for a given beam spot size. The ion-optical properties of those systems have been calculated with allowance for chromatic and spherical third-order aberrations. Regions in short and long systems are indicated where the demagnification-to-aberration ratio is optimum, providing the largest emittance.

THE INFLUENCE OF ADDITIONAL ABSORPTION ON THE ACOUSTICAL INDICATORS OF A HALL/PAPILDOMOS ABSORBCIJOS ĮTAKA SALĖS MODELIO AKUSTINIAMS RODIKLIAMS

The influence of the slits between the walls and the floor of the model upon the objective acoustical indicators was examined in a scaled model of a hall. The Small Hall of the Lithuanian National Philharmonic Society was selected for the investigations. The hall is of rectangular form, 13.6 m in length, 10.7 m in width and 7 m in height. The hall model was scaled 1:25. The floor and the ceiling of the model were made of cloth-based laminate, while the walls of plywood 8 mm thick, with three layers of varnish. Thus, all materials employed in the model were similar to those of the real hall by their sound-absorption properties. There were 1 to 3 mm slits between the floor and the walls of the model. Their overall length was about 10–12 m (converted to real values). A spark sound source was used for the radiation of signals within the required spectrum. The sound source was put through a hole in the floor in order to improve the directivity diagram of the radiation. The positions of both the source and the ¼ microphone coincided in all cases. The frequencies examined fell in the range between 1250 Hz and 50000 Hz. The frequency of quantization of the signal was 166.6 kHz and the quantization time was 6 mcs. All frequencies were converted into real ones in the diagrams. A 2000 Hz upper limit was established to ensure that the Nyquist frequency exceeds 3. The experiments showed that the slits in the model influenced the muffling of the sound energy starting from 200 ms. With the slits present, the muffling occurs faster and the greatest difference of 2–3 dB is observed in the interval of 1000—2500 ms. Given small slit dimensions and overall slit length, the change of 2-3 dB is quite significant. The muffling of the sound field of the model is not exponent in character. The muffling varies on differently in different time intervals. Then the reverberation times of a non-filtered signal must be different when the muffling is approximated every 10 dB. The investigation showed that, with the slits present, the reverberation time values were reduced by 0.4–0.8 s throughout the interval when the muffling was approximated every 10 dB, starting from 0 to—30 dB and from—5 to—35 dB. This means that the slits absorb the sound energy on all intervals of the muffling of the sound field. The largest sound absorption is reached when the muffling of the sound field is approximated every 10 dB from 0 to—30 dB and amounts to as much as 3-6 m2. The influence of the slits is weaker when the muffling is approximated on other intervals. The slits also produce effect upon subjective acoustical indicators of a non-filtered signal, which vary between 1 to 2 dB. This shows that the intensity of reflections is changed in various time intervals by the slits. The influence exerted by the slits over the early reverberation time manifests itself both at the low and high frequencies. The greatest difference of about 0.8 s is observed at 100 Hz and 160 Hz. Within the frequency range from 500 Hz to 1000 Hz, the difference is not so marked and amounts to about 0.5 s. Within the range from 200 Hz to 400 Hz, the early reverberation time is only slightly influenced by the slits. The effect produced by the slits on the standard reverberation time, as compared with the early reverberation time, is not significant up to 160 Hz, while in the frequency range of 200—2,000 Hz the standard reverberation time is cut by about 0.4–0.6 s. The smallest sound absorption brought about by the slits is observed at low frequencies (around 1 m2). In the frequency range of 200—500 Hz, the sound absorption amounts to 3–4 m2, and at the frequencies exceeding 630 Hz to 2–7 m2. At low frequencies, the music sound clarity index is increased by the slits by about 0.5 dB. From 200 Hz and on, the clarity index is increased by 2 to 4 dB. These results show that the slits in the model alter the intensity of the early sound reflections. Beginning with 250 Hz, the sound absorption amounts to 3.2–9.0 m2. Such absorption is already significant, therefore the slit factor must be taken into consideration while conducting investigations in the hall model.