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The development of epithelial lumens in ducts is essential to the functioning of various organs and in organogenesis. Ductal elongation requires the collective migration of cell cohorts in three-dimensional (3D) confined spaces, while maintaining their epithelial integrity. Epithelial lumens generally adopt circular morphologies, however abnormalities in complex physiological environments can lead to the narrowing of glandular spaces that adopt elongated and slit-like morphologies. Here, we describe a simple method to form epithelial tissues in microchannels of various widths (100-300 µm) with a constant height of 25 µm that mimic elongated geometries of glandular spaces. The significance of this biomimetic platform has been evidenced by studying the migration of epithelial cell sheets inside these narrow slits of varying dimensions. We show that the growth of epithelial tissues in 3D-confined slits leads to a gradient of cell density along the slit axis and that the migration cell velocity depends on the extent of the spatial confinement. Our findings indicate that nuclear orientation is higher for leader cells and depends on the slit width, whereas YAP protein was predominantly localized in the nucleus of leader cells. This method will pave the way to studies aiming at understanding how 3D-confined spaces, which are reminiscent of in vivo pathological conditions, can affect the growth and the homeostasis of epithelial tissues.

The influence of the conditions of mask-based photopolymerization of thick layers of a composition (with thickness h from 0.5 to 4.0 mm) based on dimethacrylate OCM-2 and o-quinone photoinitiator on the geometry of the resulting polymer sample has been studied. Upon photopolymerization of layers through a slit aperture of width l, the polymer formed has a cross section of trapezoid, the large base of which faces to the side of illumination. With increasing exposure, the difference in the sizes of the bases of the trapezoid decreases, which reduces roughness of an object composed of such layers. For stereolithographic synthesis of a 3D model from layers with h = 0.5 and 1.0 mm and roughness of 10 μm, the minimum slit width is achieved at l ≈ 2h.

Relative Response Factors (RRFs) can be used for quantitation of one compound against another and it is widely used for Impurity analysis of pharmaceutical products; however, the application in potency assay is limited. Through an extensive study shown in this paper, it can be concluded that using the “RRF methodology” for potency assay is much more challenging compared to impurity analysis, due to the much tighter criteria required for potency analysis. The effects of instrument settings, which are rarely discussed or recognized in current HPLC analytical method development and quality release testing, are discussed. These factors impact the RRF just as much as other commonly recognized HPLC parameters. The effects of UV detector settings, i.e. Slit Width, Step Width, Band Width, and Data Collection Module, have been explored. This phenomenon has been demonstrated using three compounds to observe the impact of their quantitation due to the significant RRF variations. Finally, principles to reduce RRF variations have been discussed, and practical considerations of RRF application to method development and method transfer are provided.

The critical temperatures of bulk and confined atomic fluids are investigated using values of the vapour−liquid interfacial free energy of coexistence obtained from grand-canonical transition-matrix Monte Carlo simulations using a histogram reweighting technique. The temperature corresponding to zero interfacial free energy of coexistence is the estimated critical temperature for the system under investigation. Slit width of confined atomic fluid for this investigation is varied from 40 to 1 fluid particle diameter. The obtained critical temperatures have shown nonlinear monotonic trend with inverse of slit width. Moreover, five different linear regimes of critical temperature are observed in the studied range of slit width. Interestingly, in the slit width range of less than two fluid particle diameters, the critical temperature approaches two-dimensional value and remains approximately indifferent with a decrease in slit width up to one fluid particle diameter. This investigation also reveals th...

Time-gated Raman system has been assembled using a pulsed laser and high-resolution echelle spectrograph. Echelle spectrograph provides broad spectral band-pass of 0–8500 cm�1 in a single scan with a resolution of 1.75 cm�1 for 532 nm at an extremely small slit width of 10 μm. Advantages of gated mode detection over continuous-wave mode detection are improved signal-to-noise ratio, reduced background signal, and unwanted fluorescent emission. Feasibility of echelle spectrograph for Raman measurements has been tested for both conventional and standoff distance of 5 m with all the external illumination sources on. The echelle system provides high-quality Raman signals with an extremely low inherent bandwidth in solid and liquid samples, (~8 cm�1 ) for 478 cm�1 fundamental band of sulfur. Intensity ratio of e2 fundamental to a1 fundamental of conventional and remote Raman measurements indicates that the spectral features remain the same in both measurements. The advantages of ‘time-gated’ Raman compared with continuous-wave mode detection, like low background even under extraneous illumination and lowered fluorescence, are also illustrated with spectrum of sulfur taken in the two modes.

The present work deals with the broadening of rotational lines of the carbon monoxide 2–0 band by both argon and hydrogen chloride. A high resolution grating spectrometer with a spectral slit width of 0.07 cm(−1) was used, necessitating only a small correction in observed half-width values. Sufficiently small contributions of CO self-broadening were obtained by using long pathlength cells of 12 meters for CO-argon mixture and 1 meter for CO-HCl mixture. Half-width results, which are considered accurate to within ±5 percent, are presented in the form of a table and by a graph.

We study, in this paper, the physical properties of water confined between two parallel graphene plates with different slit widths to understand the effects of confinement on the water structure and how bulk properties are reached as the water layer thickens. It was found that the microscopic structures of the interfacial liquid layer close to graphene vary with the slit width. Water tends to locate at the center of the six-membered ring of graphene planes to form triangular patterns, as found by others. The narrower the slit width is, the more pronounced this pattern is, except for the slit width of 9.5 A, for which a well-defined two-layer structure of water forms. On the other hand, squared structures can be clearly seen in single snapshots at small (6.5 A and 7.5 A) but not large slit widths. Even at small slit widths, the square-like geometry is observed only when an average is taken for a short trajectory, and averaging over a long time yields a triangular pattern dictated by the graphene geometry. We estimate the length of time needed to observe two patterns, respectively. We also used the two-phase thermodynamic model to study the variation of entropy of confined water and found that at 8.5 A, the entropy of confined water is larger than that of bulk water. The rotational entropy of confined water is higher than that of bulk water for all slit widths due to the reduction of the hydrogen bond in the confined space.

We study the conformational behavior of spherical polyelectrolyte brushes in the presence of monovalent and trivalent counterions in a confined environment. The confinement is exerted by two parallel walls on the brushes. The enhancement of the confinement induces the extension of grafted chains. For the monovalent case, the increase of the charge fraction leads to extended brush conformation for different slit width (distance between two walls) but collapsed brush in the presence of trivalent counterions is observed. The confinement does not affect electrostatic correlation between trivalent counterions and charged monomers. However, it was found that narrow slit width contributes to stronger electrostatic correlation for the monovalent case. This is because more monovalent counterions are inside the brush at strong confinement, but almost all trivalent counterions are trapped into the brush independently of the slit width. The diffusion of counterions under the confinement is related to the electrostatic correlation. Our simulations also reveal that the brush thickness depends on the slit width nonlinearly.

Understanding the translocation of soft, conformable single-chain polymer nanoparticles (SCNPs) with intricate topology through nanopores and nanoslits is of great interest for several potential applications, including modern single-molecule analytical characterization methods. This work focus on the ultrafiltration of an elastic SCNP of size R through a cylindrical pore of diameter D « R or a rectangular slit of width H « R under an elongational flow field. Concerning SCNP ultrafiltration through nanopores of different diameter, we find a scaling law in qualitative agreement with recent results concerning the ability of soft conformable nanoparticles to translocate through pores at least tenfold smaller in size. Moreover, SCNP ultrafiltration through rectangular nanoslits provides a simple way to determine the elasticity parameter of a real SCNP based on its experimentally determined minimum slit width for effective ultrafiltration., Financial support by the Spanish Ministry “Ministerio de Economia y Competitividad”, MAT2015-63704-P (MINECO/FEDER, UE), the Basque Government, IT-654-13, and the Gipuzkoako Foru Aldundia, Programa Red Gipuzkoana de Ciencia, Tecnología e Innovación 2017 (RED 101/17), is acknowledged. J.R.-C. is grateful to the Materials Physics Center MPC for his predoctoral grant. E. G. received funding from the “Fellows Gipuzkoa” fellowship of the Gipuzkoako Foru Aldundia.

We look into the electrostatic screening in ionic liquids through the calculations of structural profiles and surface forces inside the slit system with varying width. The strong ion-ion correlation is modeled with ion pair association using reaction-based classical density functional theory. The equilibrium densities and ion pair fraction are solved iteratively. For pure ionic liquids, the oscillation of charge density is damped over relatively short range while surface force decays exponentially in the long range. Pair fraction approaches the bulk value asymptotically with growing slit width. Different components of surface force are identified according to various types of interactions.

The results of investigations of the absorption of thermal radiation from a combustion site by a radial water shield are presented. The dependence of the screening coefficient on the scattering slit width has been established. It is confirmed experimentally that the screening properties of water depend on the composition of the combustion site products.

An approach has been developed to calculation of the Irving-Kirkwood pressure tensor inside a circular plane-parallel empty slit between bodies with dispersion forces. The disjoining pressure is determined as the normal component of the pressure tensor on a slit wall and is found as a function of both the width and radius of the slit. It has been shown that, at a preset slit width, the disjoining pressure acquires a value almost equal to that inherent in an infinitely long slit already at a circular slit radius five times larger than the slit width.

Aims: A simple RP-TLC Spectrodensitometric method was developed for determination of Hyoscine N-Butyl Bromide (HBB) and Paracetamol (PAR) either in bulk powder or in their pharmaceutical preparation. Study Design: Validation study. Methodology: In this method, HBB and PAR were separated on RP-18 W/ UV254 TLC plates using developing mobile phase consisting of methanol: citrate buffer (pH=1.5): triflouroacetic acid (70:30:0.1, by volume) at room temperature. Experimental conditions such as band size, slit width, different developing systems and scanning wavelength were carefully studied and the optimum conditions were selected. The obtained bands were then scanned at 210 nm. The two drugs were satisfactorily resolved with RF 0.60 ± 0.02 for HBB and 0.81 ± 0.02 for PAR. The validation of spectrodensitometric method was done regarding linearity, accuracy, precision, and specificity. Results: Linearity of the proposed methods was evaluated and it was found to lie within the concentration range of 2.0-12.0 µg.band-1 for HBB and 2.0-14.0 µg.band-1 for PAR. Conclusion: The proposed method was successfully applied for determination of HBB and PAR in pure form and in their different pharmaceutical formulations. The method proved to be specific, accurate and selective.

Corresponding states vapour–liquid phase equilibria of confined square-well fluid are studied by means of grand-canonical transition-matrix Monte Carlo simulation and histogram reweighting method. In this study, square-well fluid is considered under hard and attractive slit pore confinements ranging from 1.5 to 40 molecular diameters. Corresponding states vapour–liquid phase coexistence envelopes display insignificant effect of wall−fluid interaction for slit pore confinements ranging from 1.5 to 3 molecular diameters. On the other hand, significant effect of wall−fluid interaction on the corresponding state coexistence envelope is observed for slit pore confinements ranging from 4 to 40 molecular diameters. Moreover, at a given slit width, shrinking in corresponding state coexistence envelope is observed with increase in the wall−fluid interaction. However, in the larger slit pore width of 30 to 40 molecular diameters, shrinking in the corresponding state vapour–liquid coexistence envelopes become indifferent with the stronger wall−fluid interactions studied in this work. Structural behaviour of coexisting phases in slit pores are also investigated through local density profiles, to understand the overall behaviour of corresponding states coexistence envelopes. Fluctuating positive and negative deviations in the corresponding state spreading pressure with respect to corresponding bulk value is observed for studied wall−fluid interactions and slit pore confinements.

Molecular dynamics simulations are performed to investigate the phase behaviour of the Lennard-Jones (LJ) particles confined to slit pores with width h. For (in reduced unit based on the LJ paramet...

A high-performance thin-layer chromatographic method was developed and validated for simultaneous determination of thiocolchicoside and ketoprofen in combined dose tablet formulation. The chromatography was performed on pre-coated silica gel 60 F 254 plates using methanol-toluene-benzene 2.5:3.5:4.0 (v/v/v ) as mobile phase. The plates were developed to a distance of 8.0 cm at ambient temperature. Experimental conditions such as band size, chamber saturation time, migration of solvent front, slit width, etc. were critically studied and the optimum conditions were selected. A TLC scanner set at 260 nm was used for direct evaluation of the chromatograms in reflectance/absorbance mode. The drugs were satisfactorily resolved with R F 0.34 for thiocolchicoside and 0.65 for ketoprofen. Method was validated according to the ICH guidelines The calibration plot was linear between 125-750 ng per band for THC and 1000-6000 ng per band for KET. The LOD and LOQ for THC were 17.43 and 52.82 ng per band, for KE...

Miniaturisation of metallic structures has become a prime issue and to meet high demand, modern fabricators extensively use different micro machining techniques. Wire electrochemical machining (wire ECM) is such a process of removing excess material electrochemically. However, the process is still new and further research is needed. Hence, the present work aims in developing suitable wire ECM setup to find out the influence of wire feed rate at varying voltage settings on corresponding width of the generated microslits. For this, experimentations have been carried out with 50 μm dia tungsten wire and machined micro features have been carefully observed under optical microscope. Additionally, the experimental results have been represented graphically where the minimum average width of the microslit is found to be 83.117 μm with an aspect ratio of 1.2. Moreover, complex microfeature with varying width has been fabricated by changing corresponding feed values in a single run.

Grand-canonical transition-matrix Monte Carlo (GC-TMMC) simulation, is used to investigate the effect of pore shape and surface-fluid strength on the vapor–liquid phase transition and crossover behavior of critical properties from 3D to 2D of a square well (SW) fluid. We present the vapor–liquid coexistence phase diagram in hard and attractive cylindrical pores of varying slit width from 4 to 50 molecular diameters. This investigation indicates that having same pore shape but different surface nature can significantly alter the coexistence envelopes and hence the critical point. Critical temperature is found to approach the 3D bulk value monotonically irrespective of the pore shape and surface nature. However, the rate of approach of critical point towards the 3D bulk value decreases as the effective confinement increases. On the other hand, approach of pore critical density towards the bulk 3D value follows a non-monotonic path, irrespective of pore shape and surface strength. Interestingly, with the same pore shape, attractive wall surface follows an opposite trend to approach the bulk critical density as compared to that of hard wall surface. Crossover from 3D to 2D behavior in the hard cylindrical pores is observed around 28 molecular diameters, which is significantly larger than that observed by earlier workers for hard and attractive slit pores.

We provide measurements of Young’s double-slit experiment using a partially-coherent light source consisting of a helium-neon laser incident on a rotating piece of white paper. The data allow a quantitative comparison with both the standard theory that does not account for the width of the slits, and a full, analytic model that does. The data agree much more favorably with the full calculation.

We performed molecular dynamics simulations of Lennard-Jones particles confined in a parallel slit pore. When a slit width h was 2 σ - 6 σ , the frozen LJ particles had an hcp structure and two different axes of an fcc structure depending on the slit width. We estimated the freezing/melting point when the LJ fluid was cooled/heated, and observed an abnormality in the freezing/melting point corresponding to the difference in the crystal structure for the first time, which agreed with the results of the Clausius–Clapeyron equation. We found new crystal structures and proposed the complex h - T phase diagram.

An important step in the validation of an analytical procedure is the study of its robustness. In the case of spectrofluorimetric determinations, quenching introduces specific problems which are approached in this paper for the particular case of tetracyclines determination in milk. Quenching can be detected with excitation emission matrices (EEM) signals and a three-way Parallel Factor (PARAFAC) decomposition and modelled by means of a four-way PARAFAC decomposition which reproduces the physical model of this effect. The robustness of the method is evaluated by including changes in seven experimental variables: trichloroacetic acid (TCA) volume solution used in the precipitation of milk proteins, revolutions per minute, time and temperature in the centrifugation step, pH and emission–excitation slit width in the fluorimetric analyte determination and the analyst. The robustness analysis is carried out by means of a Plackett–Burman experimental design as it is suggested by European Decision 2002/657/EC (European Decision (EC) No. 2002/657/EC of 12 August 2002, implementing Council Directive 96/23/EC, concerning the performance of analytical methods and the interpretation of results, Off. J.L 221, 17/8/2002, 8). The analyte concentration will be taken as response in the Plackett-Burman experimental design instead of the signal as it is habitual in these cases. Therefore, a three-way Partial Least Squares (3-PLS) calibration models with EEM signal is needed. When an analogous study is carried out for tetracycline (TC) in the absence of chlorotetracycline (CTC) as interferent, univariate calibration is employed, being able to conclude that in the robustness analysis, different factors are significantly active when quenching exists.

International audience; The isosteric heat of the carbon dioxide adsorption on activated carbon is determined by grand canonical Monte Carlo simulations. The results, obtained at room temperature and low pressures for an adorbent model with a slit type porosity, show that the isosteric heat depends strongly on the slit width. The maximun of the isosteric heat is reached for a pore with a width such as cooperative effects between the adsorbed molecules enhance the adsorption. The possibility to estimate the isosteric heat of a macroscopic sample, from adsorption isotherms computed for a distribution of slit pores with given sizes, is discussed.

Duloxetine hydrochloride is a potent dual reuptake inhibitor of serotonin and norepinephrine used to treat major depressive disorders. The present work describes a simple, precise and accurate HPTLC method for its estimation as bulk and in tablet dosage form. The chromatographic separation was carried out on precoated silica gel 60 F254 aluminium plates using mixture of chloroform:methanol (8:1 v/v) as mobile phase and densitometric evaluation of spots was carried out at 235 nm using Camag TLC Scanner-3 with win CAT 1.3.4 version software. The experimental parameters like band size of the spot applied, chamber saturation time, solvent front migration, slit width etc. were critically studied and optimum conditions were evolved. The drug was satisfactorily resolved with Rf value 0.11+/-0.01. The accuracy and reliability of the proposed method was ascertained by evaluating various validation parameters like linearity (40-200 ng/spot), precision (intra-day RSD 0.46-0.75%, inter-day RSD 0.46-1.59%), accuracy (98.72+/-0.20) and specificity according to ICH guidelines. The proposed method can analyse ten or more formulation units simultaneously on a single plate and provides a faster and cost-effective quality control tool for routine analysis of duloxetine hydrochloride as bulk drug and in tablet formulation.

The pressure dependence of a 129 Xe chemical shift (δ) and the local density of xenon adsorbed in activated carbon fiber (ACF) with slit-pore widths of 11.71.I nm was investigated using in-situ high-pressure 129 Xe NMR. 129 Xe chemical shift values below 0.025 MPa change linearly with equilibrium pressure. The initial slope of the pressure dependence of δ led to a shift value at zero pressure, δ s ', which approximately reflects the xenon-wall interaction. A statistical model incorporating the xenon-wall interaction well interprets the dependence of δ s ' on the pore width. Furthermore, in a higher-pressure region, the density dependence of the chemical shift led to the xenon-xenon interaction via the virial coefficients of the chemical shift up to the second order on density (the third-virial coefficient). The second-virial coefficient (a coefficient for the linear term of density) depended on the pore width. Increasing the slit width from 0.7 to 1.1 nm increased the second-virial coefficient, δ 1 , from 42 x 10 -3 to 78 x 10 -3 ppm kg -1 m 3 , suggesting that the space accessible by the surrounding xenon atoms increases when the slit width increases. This aspect reveals the size effect of the xenon-xenon interaction in nanospace.

Efavirenz inhibits the activity of viral RNA-directed DNA polymerase (i.e reverse transcriptase). The present work describes a simple, precise and accurate HPTLC method for its estimation as bulk and in tablet dosage form. The chromatographic separation was carried out on precoated silica gel 60F254 aluminium plates using mixture of chloroform: ethyl acetate (9:1 v/v) as mobile phase and densitometric evaluation of spots was carried out at 247 nm using Camag TLC Scanner-3 with win CAT 1.3.4 version software. The experimental parameters like band size of the spot applied, chamber saturation time, solvent front migration, slit width etc. were critically studied and optimum conditions were evolved. The accuracy and reliability of the proposed method was ascertained by evaluating various validation parameters like linearity (1000-5000 ng/spot), precision (intra-day RSD 0.66-1.44%, inter-day RSD 0.87-1.42%), accuracy (98.07 to 99.07 %) and specificity according to ICH guidelines. The proposed method can analyze eight or more formulation units simultaneously on a single plate and provide a faster and cost-effective quality control tool for routine analysis of efavirenz as bulk drug and in tablet formulation.

We have examined the critical adsorption transition for a nonreversible random walk chain (NRRW) and a self-avoiding walk chain (SAW) at the surface and have identified the critical adsorption point. We then examine the partition coefficient of a NRRW chain and a SAW chain confined in a slit with two adsorbing walls near the critical adsorption point. For a NRRW chain, the partition coefficient at the critical adsorption point is equal to one and is independent of the chain length. This property has been utilized in the liquid chromatography operated at the critical adsorption point (LCCAP). For a SAW chain, however, the partition coefficient at the critical adsorption point K er is greater than one and is dependent on the chain length and slit width. This confirms the experimental observation of a weak chain length dependence of the partition coefficient at the critical point. Moreover, the study found that K er for a SAW scales with (R g0 /D 2 ) to a first-order approximation where R g0 is the radius of the gyration of the unconfined chain in the dilute solution and D is the slit width.

Confined systems exhibit interesting properties that are applied to the fields of lubrication, adhesion and nanotechnology. The replica exchange molecular simulation method was applied to calculate the phase equilibrium points of Lennard–Jones particles in a two-dimensional confined system. The liquid–solid phase equilibrium points and the solid structure with a dependency of the slit width were determined and the order parameter of the solid structure was analyzed. Such confined systems are shown to be favorable for manipulation of the phase equilibrium points.

Using a setup based on fluorescence microscopy we study fluorescence spectra of single chromophores. Being point like emission sources single molecules can be focused to the entrance slit of a spectrometer. Even with narrow slit width the light passes the system with almost no loss. We show that, making full use of the emission properties of a single molecule, fluorescence spectra of many single molecules can be recorded simultaneously using (hyper-)spectral imaging. The vibrational frequencies of the single terrylene chromophores in naphthalene are the same within the accuracy of our experiments but the vibronic lines show pronounced differences in their relative intensities.

A previously developed method (Hag and Schatzki 1993) for detecting pits in red tart pitted canned cherries was expanded to detect pit fragments as well. fie cherries were pulped in a modified kitchen blender and poured into a slit sieve designed with an adjustable slit width to let the cherry pulp wash through while retaining the pits and fragments. Some further fragmentation of pit fragments occurred during blending (3-5.5%), but can be corrected for. With an optimized slit width of 1.5 mm, 79% offragments were caught by the sieve and thus detected, independent of fragment length. Passage of fragments followed a binomial distribution. fiis method, while not an on-line one, uses exceedingly simple and inexpensive equipment and is ideally suited for field testing.

Computer simulations and density functional theory results are reported for a Lennard-Jones liquid in a slit or pore formed by two parallel hard walls. Both density profiles and solvation forces are computed. Two classes of calculation are performed. In the first class, a high bulk density is selected and, starting from a high temperature, the temperature is reduced until the temperature corresponding to bulk liquid—vapour coexistence is reached. For small slit widths or exceedingly large widths, the density in the slit decreases continuously until the slit is virtually empty or ‘dry’. When the slit width is somewhat larger than a molecular diameter, but still finite, the density in the slit decreases continuously as the temperature is decreased until there is an abrupt change in the density in the slit. Below this temperature, the density is smaller. Further decreases in the temperature, result in a continuous decrease in the slit density until the slit is virtually empty. In the second class, the densit...

Ultraviolet (UV) transmission spectra of UV-absorbing hydrogel contact lenses have been reported in the literature. Few of these studies were done following ANSI or ISO specified procedures. These published procedures do specify an integrating sphere in the detector system and a beam size, but not other instrument settings such as slit width, spectral smoothing functions, and scan speed. This work, done with Acuvue R and Precision UV TM contact lenses, shows that an integrating sphere is needed to ensure the accuracy of the data. A smaller beam size than specified was required to obtain accurate spectra. A slit width larger than recommended by the spectrophotometer’s manufacturer was needed to increase precision. Spectra results were unaffected by scan speed and spectral smoothing settings.

Root hairs substantially extend root surface for ion uptake. Although many reports suggest a relationship between root hairs and phosphorus (P) uptake of plants, the role of root hairs in phosphorus uptake from soils is still debated. We measured uptake of phosphorus from soil directly via root hairs. Root hairs only were allowed to penetrate through a tightly stretched nylon screen (53 µm) glued to the bottom of a PVC tube. The penetrating root hairs grew for 2 and 4 days in soil labelled with radioisotope phosphorus (P) tracer 32P (185 kBq g-1 dry soil) filled in another PVC tube. Transparent plastic rings of thickness ranging from 0.25 mm to 2.0 mm were inserted between the two PVC tubes. This provided slit width for microscopic observations in situ, which confirmed that only root hairs were growing into the 32P labelled soil. In some cases no rings were inserted (slit width = 0) where both root hairs and root surface were in contact with the labelled soil (total 32P uptake). The uptake of32 P from soil via the root hairs only was quantified by measuring activity of 32P in the plant shoot (32P uptake only via root hairs). The results showed that when 70 percent of the root hairs grew into the labelled soil, they contributed to 63 percent of the total P uptake. With decreasing number of root hairs growing into the 32P labelled soil, the quantity of 32P in the plant shoot decreased. In this study, P uptake via root hairs was measured in a soil-based system, where root hairs were the only pathway of 32P from soil to the plant shoot. Therefore, this study provides a strong evidence on the substantial participation of root hairs in uptake of phosphorus from soil.

We present a lattice computer simulation study on the geometrical confinement effect of polymer solutions in a wide range of concentrations. Polymer chains were equilibrated for a system that consists of a bulk solution and a slit between two parallel walls. The partition coefficient of the polymer was determined and found to increase as the bulk concentration Φ increased, confirming the theoretical predictions. We applied the blob picture to analyze the partition coefficient data in the semidilute regime where the partitioning is considered to be controlled by the ratio of the blob size to the slit width, rather than by the ratio of the chain dimension to the slit width. Our simulation data and earlier experimental data support the application of the blob theory. Furthermore, we found it is possible to estimate the blob size in the bulk solution directly from the partition coefficient data by assuming that the confinement entropy of the blob depends on the blob size in the same way as the confinement entropy of the individual chain depends on the chain dimension at infinite dilution. The blob size thus determined confirms the scaling prediction; namely, the blob size ∞ Φ -3/4 . Some deviations from this simple picture, however, exist when the slit is narrow and the solution is concentrated.

This paper presents a comparison of quantification of thin-layer chromatographic plates with slit-scanning densitometry and with two image-analysing systems. Camag test dye mixture III was used as a sample. The influence of different measuring beam dimensions (slit width and slit length) on the quantitative evaluation of thin-layer chromatograms was studied in the reflectance as well as in the transmission mode. The slit length has a much higher influence on the reproducibility of the measured areas than the slit width. The results obtained with both CCD cameras show linear correlation between response area and concentration of Camag test dye mixture III in a higher concentration range than the densitometrically obtained results. The sensitivity of the used image-analysing systems was much lower than that of the slit-scanning densitometer.

A simple technique for estimating the slit width of a spectrometer from the ratio of the observed (Δν1/2)R and (Δν1/4)R of a Raman line profile was developed by calculating a set of corresponding values of Z=(Δν1/4)R/(Δν1/2)R and X=S/(Δν1/2)R based on the exact numerical evaluation of the Voigt profile. This technique was applied to some selected Raman lines and was found to give accurate values of the slit width in almost all cases where the slit distortion is appreciable and the band is isolated. Another technique for calculating the fractional Lorentzian character from the observed Raman spectra is also suggested. © 1997 by John Wiley & Sons, Ltd.

After studying the factors of how, the slit width of a slitted bluff-body (SBB) burner influences the cold state flow field, the hot state temperature and gas concentration fields. the following important conclusions are obtained: the slit width influences not only flow characteristics behind the slitted bluff-body such as the size and reflux rate of the recirculation region. but also the quantity of pulverized coal jetting into it. To use it in an industrial plant, the optimal value of slit width is determined as about 10 percents of the width of the bluff-body (BB).

In order to determine the bluff body and slitted bluff body flame stability and combustion performance, atmospheric low-speed experimental platform is used to carry out diesel fog combustion experiment for comparison of two types of bluff body, which are respectively streamlined V-form added straight channel and triangle V-form added straight channel. Results have shown that under the same condition, nonslit triangle bluff body burns better than nonslit streamlined bluff body. In another case, slitted triangular bluff body is still better than the slitted streamlined bluff body in combustion performance if the slit width ratio is selected appropriately (δ/B = 14%). In the case of relatively large slit width ratio (δ/B=29%), the opposite conclusion is obtained, which is that slitted streamlined bluff body is better than the slitted triangular one in combustion performance.

The R branch of the nu(5)-nu(4) difference band of acetylene, 12C(2)H(2), is recommended as a calibration standard for the 100-200-cm(-1) region. The lines are split by l-type doubling into pairs with a 3:1 intensity ratio, but this can only be observed under high resolution. The position of the calculated maximum of each blended line contour is displaced by the l-type doubling from the accurately calculated wavenumber of the more intense component of each J pair, but not by more than one-fifteenth of the spectral slit width. It is recommended that values calculated from constants derived from high resolution mid-ir measurements be used for calibration.

The silicate layers of montmorillonite clay were pillared with SiO2–TiO2 sol particles. Although only the SiO2 sols were negatively charged, the SiO2–TiO2 mixed oxide sols were positively charged and could be ion-exchanged with the interlayer cations of montmorillonite. The resulting pillared clays had a basal spacing expanded to more than 40 A; the spacing was maintained during calcination up to 773 K. The adsorption properties of the calcined samples were studied for nitrogen as well as organic vapors. A structural model for the arrangement of the intercalated sol particles is proposed in which small SiO2–TiO2 sol particles are packed between the silicate layers. Micropores with a slit width of 10–12 A are formed in the interstices between the sol particles and the silicate layers.

A method is described to avoid the effects of sample heterogeneity in Raman measurements on solid samples. A Hadamard multiplex multichannel system with a bifurcated fiber-optic bundle for excitation and collection is used. The Hadamard mask employs a 7-element code with a unit slit width of 400 μm. Results are reported for samples prepared by mixing cytosine and 5-methylcytosine powders.

The noise penalties of the following resolution-enhancement procedures are compared: (a) deconvolution when the apparatus function is smooth, (b) deconvolution when the apparatus function possesses a step discontinuity, and (c) physically reducing the experimental “slit width” or its equivalent. It is shown that it is not feasible to very significantly increase resolution by deconvolution when the apparatus function is smooth. The method (c) achieves a given resolution increase with the smallest noise increase of these methods. However, method (b) is feasible when the source distribution possesses a discontinuity, and the apparatus resolution is good. This occurs naturally when using a field emission source in electron energy loss spectroscopy. Using the Fermi-level cut-off as a discontinuity in the source distribution, we use method (b) above to obtain deconvoluted data which is limited only by the spectrometer resolution.

We have proposed an integrated Fresnel lens with multiple slits in a Si slab waveguide. The slit width and the slit spacing were optimized and the integrated lens had a reflective loss of 0.38 dB.

To investigate the internal structure changes in virgin black human hair keratin fibers due to aging, the structure of cross-sections at various depths of virgin black human hair (sections of new growth hair: 2 mm from the scalp) from a group of eight Japanese females in their twenties and another group of eight Japanese females in their fifties were analyzed using Raman spectroscopy. For the first time, we have succeeded in recording the Raman spectra of virgin black human hair, which had been impossible due to high melanin granule content. The key points of this method are to cross-section hair samples to a thickness of 1.50-microm, to select points at various depths of the cortex with the fewest possible melanin granules, and to optimize laser power, cross slit width as well as total acquisition time. The reproducibility of the Raman bands, namely the alpha-helix (alpha) content, the beta-sheet and/or random coil (beta/R) content, the disulfide (--SS--) content, and random coil content of two adjoining cross-sections of a single hair keratin fiber was clearly good. The --SS-- content of virgin black human hair from the Japanese females in their fifties for the cortex region decreased compared with that of the Japanese females in their twenties. On the other hand, the beta/R and alpha contents of the cortex region did not change.

We use few-body methods to investigate the diffraction of weakly bound systems by a transmission grating. For helium dimers, He2, we obtain explicit expressions for the transition amplitude in the elastic channel.

Adsorption equilibria of methane in model micropores composed of micrographite (MG) units have been calculated by using the grand canonical ensemble MC method. Two model pores of different arrangements in MG units, MG-parallel and MG-honeycomb, are considered. The amount of methane adsorbed in the two micropores is found to be smaller than that in the slit pore with infinite parallel graphite planes; however, it is suggested that an MG-honeycomb pore could adsorb more methane when the interaction of edge carbons with methane is stronger than that of the inner carbons.

The silicate layers of montmorillonite clay were pillared with SiO2–TiO2 sol particles. Although only the SiO2 sols were negatively charged, the SiO2–TiO2 mixed oxide sols were positively charged and could be ion-exchanged with the interlayer cations of montmorillonite. The resulting pillared clays had a basal spacing expanded to more than 40 A; the spacing was maintained during calcination up to 773 K. The adsorption properties of the calcined samples were studied for nitrogen as well as organic vapors. A structural model for the arrangement of the intercalated sol particles is proposed in which small SiO2–TiO2 sol particles are packed between the silicate layers. Micropores with a slit width of 10–12 A are formed in the interstices between the sol particles and the silicate layers.

This article reports on the separation and determination of Cr(III) and Cr(VI) with cation-exchange chromatography and flame atomic absorption spectroscopy. A sample containing the two ions is added to a column containing a cation-exchange resin; the Cr(VI) ions are not retained by the resin and are collected in the effluent. The Cr(III) ions are retained by the resin and eluted with an HCl solution. The separated ions are aspirated into an air/acetylene flame and the absorbance measurements are made at λ = 357.9 nm and 0.2-nm slit width. The experiment has been implemented in a quantitative methods of analysis course. The results of the analysis of synthetic water samples obtained by students majoring in various areas of science are presented. The data showed that 58% of the Cr(VI) and 39% of the Cr(III) values had relative errors in the range of ±5%. The evaluation of the precision of the student results revealed that 48% of the Cr(III) and 81% of the Cr(VI) reported values had RSD ≤ 4%. This experiment...

Students are introduced to screening and sequential experimentation using simulations and experimentation. The work begins with spreadsheet simulations and practice with the experimental design software. Students learn how to use the graphical output, normal quantile plots, to recognize the specific factors that affect the result of an experiment. In the laboratory, students make a preliminary investigation of the effect of six variables (flame observation height, flame stoichiometry, acetic acid, lamp current, wavelength, and slit width) on the atomic absorption signal for silver. This requires only sixteen experiments. Two or three active variables and an interaction of two variables are typically observed. Following this 26-2 fractional factorial design experiment, students investigate the effect of two active variables in more detail. This typically requires 16 to 25 experiments. The complexity of the system becomes apparent when flame observation height and percentage of acetic acid are studied. Most, but not all, of the observations are consistent with descriptive material that would be found in a typical instrumental methods text.