Large Aperture Size Research Articles

Study on heat and moisture vapour transmission characteristics through multilayered fabric ensembles

A detailed study on the heat and moisture vapour transmission characteristics of different types of single and multi-layered fabric ensemble by using sweating guarded hot plate (SGHP) has been reported in the present paper. A comparison has been made on thermal and moisture vapour transmission properties of five different insulative fabrics, namely, knitted-raised fabric, needle punched nonwoven, through air bonded nonwoven, spunbonded-through air bonded sandwich nonwoven and warp knitted spacer fabric and three different coated fabrics, namely, plain woven rubber coated, plain woven polyester polymer coated and plain woven polytetrafluoroethylene (PTFE) coated fabric, used for thermal insulation purpose. ANOVA has been conducted to analyse the significance of type of insulative and coated fabrics used. Sandwich nonwoven fabric which has higher thickness and porosity shows higher thermal resistance followed by through air bonded fabric, raised fabric, needle punched fabric and spacer fabric. Spacer fabric shows lesser evaporative resistance due to its lesser thickness and larger aperture size, which increases the diffusion of moisture vapour. Needle punched fabric shows slightly higher evaporative resistance than spacer fabric, followed by raised fabric, through air bonded fabric and sandwich nonwoven fabric. Permeability index of different multilayered fabric ensembles are also compared.

The diffraction index, its application and a brief description

People having an interest in the image quality of a lens or other optical unit used with a camera will find that there are occasions when there is a need to consider the performance of one lens in relation to another. Such an interest can arise from a simple curiosity, to a serious assessment of capabilities with an alternative system. Circumstances can, however, occur where the only information readily available to make a comparison between lenses may simply be the specification of focal length and a relative aperture, or even just the size of aperture involved. In more extreme circumstances, it may only be possible to glean some estimate of the aperture size for the optical unit or lens of interest by a close visual examination of an illustration or diagram. In such instances, it then becomes necessary to produce an initial estimate of image quality that can be based on a characteristic common to all lenses and optical systems used to produce the primary image. A characteristic that meets this requirement is that of diffraction. The phenomenon of diffraction, caused by the necessity of always having an aperture stop in the optical system, thereby becomes the attribute suggested here as a means of ranking the potential for image quality possible with a given lens or system in relation to a range of other optical systems available for the application. Diffraction, though a primary consideration when assessing image quality, is not the only significant factor to be regarded as a guide to the standard of image quality that may be involved. Details of other factors that, in an ideal world could provide further guidance to quality, are, however, not necessarily readily available when needed. As a result, and in the absence of further information, it needs to be born in mind that there will be some uncertainty as to the degree of precision expressed by any assessment based on diffraction effects alone. However, since diffraction is a fundamental feature with all optical systems, it can provide a general indication of the performance that could be expected. The numerical value for a diffraction index (DI), as described here, is given by dividing the circumference, at the maximum diameter for the aperture stop in an optical system, by the area of the aperture stop at that setting. The result of this calculation is to reduce the effect of diffraction on image quality, due to the aperture effect, in inverse proportion to the area of the aperture, in accordance with established theory and practice. For the purpose described here, the most meaningful aperture stop size to be used when calculating the DI is that indicated by the relative aperture, where the aperture size (d) is shown by the relationship: d5e/n, where e is the focal length and n is the relative aperture. Alternatively, measurement of the first glass surface in a prime lens or optical system may be used as representing the aperture stop, though the results obtained using this measurement can be misleading, for example, when optical systems with a very wide field of view are being considered. This is due to the large size of front and rear elements used in their design to ensure even illumination across the image area. In practice, there can be a divergence in the values obtained depending on which method is used in measuring, or estimating, the size of an aperture. Where a zoom lens is under consideration, then the largest aperture size indicated by the relative aperture settings must be used. It follows from this that, when calculation of the DI is expressed by a smaller index number, then the image quality can be expected to have improved. It is The MS was accepted for publication on 30 March 2011. * Corresponding author: G. H. Thomson, Strut & Thomas, 57 Winslow Field, Great Missenden, Buckinghamshire HP16 9AR, UK; email: rssat@hotmail.co.uk 65

Depth-of-Field Extension Method Using Variable Annular Pupil Division

The depth-of-field (DOF) of an imaging system is closely related to the pupil function that describes the characteristics of the pupil such as size and shape. Shallow DOF is especially problematic in microscopic optical imaging systems because they have relatively large aperture size for high optical resolution. In this paper, a new DOF extension method is proposed. This is to acquire an image by integrating the incoming light while changing the size of annular pupil. By dividing the pupil into annular form, the effect of the defocus aberration is reduced. Theoretical background is explained and simulation and experimental results are shown for verification. The results show that the DOF can effectively be extended by this method.

Young non-VDU users are more susceptible to ocular functions changes with sustained VDU nearwork

PurposeThis study investigates the change in ocular function among young schoolchildren following nearwork with and without visual display units (VDU). MethodsThirty-one young schoolchildren played computer game (VDU work) and paper game (non-VDU work) continuously for 2h at 40cm. Non-invasive tear break up time (NIBUT), blinking rate (BR) and palpebral aperture size (AS) were measured before and after VDU work and non-VDU work. Reading for NIBUT, BR and AS were normalized by converting into log10 unit. ResultsMANCOVA analysis shows that logNIBUT is significantly reduced after both nearwork (F1,49=58.10, p<0.01) but not for logBR and logAS (p>0.01). Pairwise comparison shows that modes of nearwork produce significant different effect in post-task logBR (F1,53=7.13, p=0.01) and logAS (F1,53=11.00, p<0.01). VDU work produces lower BR and larger AS while Non-VDU work does not change the BR but is associated to a smaller AS. ConclusionsSustained 2-h VDU work and non-VDU work produces significant reduction in NIBUT measurements. Modes of nearwork differently change the post-task BR and AS. Young schoolchildren are more susceptible to VDU nearwork effect.

One-dimensional neutron focusing with large beam divergence by 400mm-long elliptical supermirror

Reflective optics is one of the most useful techniques for focusing a neutron beam with a wide wavelength range since there is no chromatic aberration. Neutrons can be focused within a small area of less than 1 mm2 by high-performance aspherical supermirrors with high figure accuracy and a low smooth substrate surface and a multilayer interface. Increasing the mirror size is essential for increasing the focusing gain. We have developed a fabrication process that combines conventional precision grinding, HF dip etching, numerically controlled local wet etching (NC-LWE) figuring, low-pressure polishing and ion beam sputtering deposition of the supermirror coating to fabricate a large aspherical supermirror. We designed and fabricated an piano-elliptical mirror with large clear aperture size using the developed fabrication process. We obtained a figure error of 0.43 μm p-v and an rms roughness of less than 0.2 nm within an effective reflective length of 370 mm. A NiC/Ti supermirror with m = 4 was deposited on the substrate using ion beam sputtering equipment. The results of focusing experiments show that a focusing gain of 52 at the peak intensity was achieved compared with the case without focusing. Furthermore, the result of imaging plate measurements indicated that the FWHM focusing width of the fabricated mirror is 0.128 mm.

Expected performance of solar adaptive optics in large-aperture solar telescopes

High resolution ground based solar observations require adaptive optics correction. The next generation of solar telescopes will have large aperture sizes, in the range of 4 m, and will require larger and more complex adaptive optics systems. We study the effects that extended field wavefront sensors have on the correction performance for large aperture size telescopes. These effects are more pronounced for observations at low elevation angles, which are common during high resolution solar observations. Additionally, atmospheric dispersion is strongest at low elevation angle observations and can cause further reductions of the adaptive optics performance. We present a study of the expected correction performance of solar adaptive optics systems in large-aperture solar telescopes using an end-to-end adaptive optics simulation package.

Evaluation of calcium and hydroxyl ions release from non-setting calcium hydroxide paste and mineral trioxide aggregate during apexification procedure

Background: Several materials had been used as intracanal dressing to stimulate hard tissue formations during apexification procedure. Recently, a single appointment technique by using mineral trioxide aggregate (MTA) has been proposed as an alternative to the multiappointment calcium hydroxide apexification. The aim of this study was to evaluate the release of calcium and hydroxyl ions from calcium hydroxide paste and MTA through three different apical aperture sizes during pexification procedure. Materials and Methods: The root canals of sixty extracted premolar teeth were instrumented to a master apical file No. 100, 120, and 140 and filled with either calcium hydroxide paste or MTA. Calcium ions concentrations and pH values of the surrounding media were measured at days 1, 3, 7, 14, 21, and 28 of the test period. Results: Calcium ions concentrations and pH values of Ca(OH)2 were more than that of MTA at days 1, 3, and 7, then the calcium ions concentrations of MTA increased with time and became more than that of Ca(OH)2 which decreased with time. Ca+2 and OH-1 release from Ca (OH)2 paste and MTA increased with larger apical aperture size at all time intervals. Conclusions: MTA maintains a continuous calcium and hydroxyl ions release for longer time than that of Ca (OH)2 paste.

Adsorbate Selectivity of Isoreticular Microporous Metal–Organic Frameworks with Similar Static Pore Dimensions

Adsorbate selectivity has been investigated using three isoreticular metal–organic frameworks (MOFs) {[ML], 1 (M = Cu2+) and 2 (M = Zn2+) where L = 5-(pyridin-3-ylethynyl)isophthalate; 3 (M = Cu2+) where L = [(pyridin-3-ylmethyl)amino] isophthalate} of similar “static aperture size” but of different framework flexibility, where the MOFs have the same two different types of cagelike pores, cage A and cage B. While cage A of the MOFs with sufficiently large aperture size compared with the dimensions of the adsorbates investigated does not show any adsorbate selectivity, cage B with an approximate size match between the adsorbates and the pore apertures shows size selectivity for the adsorbates. Although the static aperture size of cage B in 3 is smaller than those in 1 and 2, the order of the “effective aperture sizes” of the cage Bs of the activated MOFs, 1a–3a, is 2a ≥ 3a ≥ 1a, which reflects the differing framework flexibility. The size selectivity of the MOFs for N2 and Ar follows the more shape-depende...

Size- and Shape-Selective Isostructural Microporous Metal–Organic Frameworks with Different Effective Aperture Sizes

Two isostructural metal-organic frameworks (MOFs) having micropores of the same "static aperture size" but different "effective aperture size" have been prepared using 5-(pyridin-3-ylethynyl)isophthalic acid as a ligand having two different types of functional units, an isophthalate (iph) unit and a pyridyl unit, simultaneously in a single ligand. The combination of iph unit and Cu (or Zn) ion led to two-dimensional layers of Kagomé (kgm) net topology, the layers being further pillared by the internal auxiliary pyridyl unit to form a three-dimensional microporous framework having two different types of cage-like pores, cage A and cage B, with different aperture sizes and shapes. (1) The MOFs can distinguish the adsorbates (N(2)/Ar) not based on the widely used kinetic diameters of the adsorbates but based on the minimum diameters of the adsorbates, which are more shape dependent. While cage A with a sufficiently large aperture size compared with the size of the adsorbates does not show any size selectivity, cage B with an approximate size match between the adsorbates and the pore apertures shows shape selectivity for the adsorbates. The smaller but spherically shaped Ar atom is not allowed into the pore with the oval-shaped aperture; however, the larger linear N(2) molecule is allowed into the pore with the oval-shaped aperture. (2) Even though the two isostructural MOFs have the same static aperture size of cage B, they show different size selectivity for the adsorbates based on the effective aperture size, which reflects the different extents of the framework flexibility.

Double-Layered Vibratory Grating Scanners for High-Speed High-Resolution Laser Scanning

A novel micromachined electrostatic double-layered vibratory grating scanner has been successfully developed for high-speed high-resolution laser scanning applications. This paper presents its design, modeling, fabrication, and measurement results. A comprehensive dynamic model considering the geometric nonlinearity of the platform suspension flexures is also proposed to predict the dynamic performance of the device at large scanning amplitudes. Compared with previously reported single-layered vibratory grating scanners, double-layered scanners - in which the diffraction grating and its driving actuator are located in different layers - have the potential to scan at large amplitudes and at high scanning speeds with large aperture sizes. We have demonstrated a prototype with a 2-mm-diameter diffraction grating which is capable of scanning at 23.391 kHz with an optical scan angle of around 33° and a resulting θopticalD product (product of the optical scan angle and diameter of the diffraction grating) of 66 deg mm.

Approximate multipole coefficients of RF ion traps as functions of aperture size

In this study we present approximate analytical expressions for estimating the variation in multipole expansion coefficients as a function of the size of the apertures in the electrodes in axially symmetric (3D) and two-dimensional (2D) ion trap ion traps. Following the approach adopted in our earlier studies which focused on the role of apertures to fields within the traps, here too, the analytical expression we develop is a sum of two terms, A n,noAperture , the multipole expansion coefficient for a trap with no apertures and A n,dueToAperture , the multipole expansion coefficient contributed by the aperture. A n,noAperture has been obtained numerically and A n,dueToAperture is obtained from the n th derivative of the potential within the trap. The expressions derived have been tested on two 3D geometries and two 2D geometries. These include the quadrupole ion trap (QIT) and the cylindrical ion trap (CIT) for 3D geometries and the linear ion trap (LIT) and the rectilinear ion trap (RIT) for the 2D geometries. Multipole expansion coefficients A 2 to A 12, estimated by our analytical expressions, were compared with the values obtained numerically (using the boundary element method) for aperture sizes varying up to 50% of the trap dimension. In all the plots presented, it is observed that our analytical expression for the variation of multipole expansion coefficients versus aperture size closely follows the trend of the numerical evaluations for the range of aperture sizes considered. The maximum relative percentage errors, which provide an estimate of the deviation of our values from those obtained numerically for each multipole expansion coefficient, are seen to be largely in the range of 10–15%. The leading multipole expansion coefficient, A 2, however, is seen to be estimated very well by our expressions, with most values being within 1% of the numerically determined values, with larger deviations seen for the QIT and the LIT for large aperture sizes.

Formulations generated from ethanol-based proliposomes for delivery via medical nebulizers

Multilamellar and oligolamellar liposomes were produced from ethanol-based soya phosphatidyl-choline proliposome formulations by addition of isotonic sodium chloride or sucrose solutions. The resultant liposomes entrapped up to 62% of available salbutamol sulfate compared with only 1.23% entrapped by conventionally prepared liposomes. Formulations were aerosolized using an air-jet nebulizer (Pari LC Plus) or a vibrating-mesh nebulizer (Aeroneb Pro small mesh, Aeroneb Pro large mesh, or Omron NE U22). All vibrating-mesh nebulizers produced aerosol droplets having larger volume median diameter (VMD) and narrower size distribution than the air-jet nebulizer. The choice of liposome dispersion medium had little effect on the performance of the Pari nebulizer. However, for the Aeroneb Pro small mesh and Omron NE U22, the use of sucrose solution tended to increase droplet VMD, and reduce aerosol mass and phospholipid outputs from the nebulizers. For the Aeroneb Pro large mesh, sucrose solution increased the VMD of nebulized droplets, increased phospholipid output and produced no effect on aerosol mass output. The Omron NE U22 nebulizer produced the highest mass output (approx. 100%) regardless of formulation, and the delivery rates were much higher for the NaCl-dispersed liposomes compared with sucrose-dispersed formulation. Nebulization produced considerable loss of entrapped drug from liposomes and this was accompanied by vesicle size reduction. Drug loss tended to be less for the vibrating-mesh nebulizers than the jet nebulizer. The large aperture size mesh (8 mum) Aeroneb Pro nebulizer increased the proportion of entrapped drug delivered to the lower stage of a twin impinger. This study has demonstrated that liposomes generated from proliposome formulations can be aerosolized in small droplets using air-jet or vibrating-mesh nebulizers. In contrast to the jet nebulizer, the performance of the vibrating-mesh nebulizers was greatly dependent on formulation. The high phospholipid output produced by the nebulizers employed suggests that both air-jet and vibrating-mesh nebulization may provide the potential of delivering liposome-entrapped or solubilized hydrophobic drugs to the airways.

Prospective Audit of Parastomal Hernia: Prevalence and Associated Comorbidities

There is little evidence regarding the prevalence or incidence of parastomal hernia, but it is thought to be common. Repair of parastomal hernia can be troublesome, and methods of repair need to be validated based on reduced incidence following surgery. The true rate of parastomal herniation needs to be determined prospectively, and risk factors for developing such hernias need to be more clearly defined. To determine prevalence and associated risk factors, prospective data were collected regarding initial stoma surgery, presence of parastomal hernia, and comorbidities. Ninety patients were prospectively audited. For stomas formed at emergency or elective surgery, regardless of surgical indication, the overall rate of parastomal hernia was 33%. Aperture size and patient age were independently predictive of parastomal hernia in multivariate analysis. For every millimeter increase in aperture size, the risk of developing a hernia increased by 10% (odds ratio, 1.10 (CI, 1.03-1.18); P = .005). For every additional year of patient age, the risk of developing a hernia increased by 4% (odds ratio, 1.04 (CI, 1.00-1.08); P = .04). There was a significantly higher prevalence of hernia following sigmoid colostomy than following ileostomy (45.9% vs. 22%; P < .05). The hernia rate was higher but did not reach statistical significance in patients with disseminated malignancy, body mass index >35 kg/m2, diabetes, prostate hypertrophy, ascites, or chronic constipation. This study of carefully and prospectively collected data shows the prevalence of parastomal herniation to be 33%. This rate was higher with larger aperture size and increased age in multivariate analysis.

Study of vibro-acoustography with high spatial resolution based on sector array transducers

This study investigates the vibro-acoustography of sector array transducers. Based on the vibro-acoustography and basic sector-array field theory, a modified and accurate velocity potential function is obtained. We further calculated and simulated the point spread function （PSF） of the system, designed the phantom of tissue, and simulated the phantom imaging. In the end, the influencing factors on spatial resolution with sector array transducers are analyzed on the basis of the simulation results. The results reveal that high resolution and contrast can be achieved, and this imaging method is of great value in detecting thermal lesion after high intensity ultrasound surgery and so on. The resolution will be improved by increasing central frequency, reducing geometric focal distance, and using transducers with larger aperture size.

Natural Convection Heat Transfer in a Partially Open Square Cavity With a Thin Fin Attached to the Hot Wall

A computational study of steady, laminar, natural convective fluid flow in a partially open square enclosure with a highly conductive thin fin of arbitrary length attached to the hot wall at various levels is considered. The horizontal walls and the partially open vertical wall are adiabatic while the vertical wall facing the partial opening is isothermally hot. The current work investigates the flow modification due to the (a) attachment of a highly conductive thin fin of length equal to 20%, 35%, or 50% of the enclosure width, attached to the hot wall at different heights, and (b) variation of the size and height of the aperture located on the vertical wall facing the hot wall. Furthermore, the study examines the impact of Rayleigh number (104⩽Ra⩽107) and inclination of the enclosure. The problem is put into dimensionless formulation and solved numerically by means of the finite-volume method. The results show that the presence of the fin has counteracting effects on flow and temperature fields. These effects are dependent, in a complex way, on the fin level and length, aperture altitude and size, cavity inclination angle, and Rayleigh number. In general, Nusselt number is directly related to aperture altitude and size. However, after reaching a peak Nusselt number, Nusselt number may decrease slightly if the aperture’s size increases further. The impact of aperture altitude diminishes for large aperture sizes because the geometrical differences decrease. Furthermore, a longer fin causes higher rate of heat transfer to the fluid, although the equivalent finless cavity may have higher heat transfer rate. In general, the volumetric flow rate and the rate of heat loss from the hot surfaces are interrelated and are increasing functions of Rayleigh number. The relationship between Nusselt number and the inclination angle is nonlinear.

Physical and Analytical Studies of Sand Production from a Supported Wellbore in Unconsolidated Sand Media With Single- and Two-Phase Flow

Abstract Use of expandable technology for sand control has rapidly grown in recent years. While several expandable systems have been developed, assessment of their long-term performance and effectiveness has hitherto not been objectively completed. To address some of the concerns and uncertainties on this front, this paper provides criteria for the assessment of sanding from wellbores completed by expandable completion techniques. It also provides an in-depth understanding of the mechanism under which expandable screens control mobilization of sand grains. A series of experiments were conducted using hollow cylinder unconsolidated sand samples. The primary objective was to assess the influence of the opening size relative to the grain size in dictating the operational limits. A stiffener, representative of a general expandable completion technique, supported the central hole. The stiffener contained a network of small perforations. Experiments were conducted on both single- and two-phase flow media. This was to explore the possible effect of a second phase in sand production in the presence of the stiffener. Experiments showed that the mobilized friction between the grains plays a major role in preventing sand production. The experiments also confirm that even with a large aperture size of an order of magnitude greater than the maximum grain size, sanding did not take place under routine operational conditions in a two-phase medium. On the contrary, instant sanding from the sandpack in single-phase experiments took place, which emphasized the important role of capillarity. Introduction Several expandable techniques have been implemented by the oil industry(1–5) and their application is experiencing a rapid growth. Although expandable completion techniques have been used in over 1,000 wellbores(6), few experimental research studies have been reported on their interaction with the medium around them. This paper bridges a gap in the literature on several important issues surrounding supported wellbores. This paper presents insights into the hollow cylindrical experimental implementation of an expandable completion and uses both single- and two-phase fluid flow. Field observations have indicated there are strong ties between sand production and water influx(7–11). A formulation is suggested for the evaluation of the stability of unconsolidated media under single- and two-phase flow conditions. The validity of the formulation is examined by experimental observations. This research used unconsolidated sand in a comprehensive experimental program. The importance of studying the response of unconsolidated and weakly consolidated sandstones to expandable completions is realized by estimations that approximately seventy percent of the total World's oil and gas reserves are found in poorly consolidated reservoirs(7). Experimental Setup The testing equipment included the loading unit, the flow setup unit, the sand weight measurement unit and instrumentation. A schematic of the testing equipment is depicted in Figure 1. A steel 12 mm thick shell restrains a hollow cylinder sample surrounded by 7.5 mm thick gravel pack. The samples were 125 mm in FIGURE 1: A schematic of the consolidation chamber (Available in full paper) FIGURE 2: Grain size distributions of the fine and coarse sand used in sandpack samples (Available in full paper) diameter and 250 mm in height.

Parametric Study of Proton-Implanted Photonic Crystal Vertical-Cavity Surface-Emitting Lasers

Photonic crystals with single- and seven-point defects are used to achieve single-fundamental-mode operation of proton-implanted vertical-cavity surface-emitting lasers. The holes are etched at a variety of depths for various photonic crystal designs to investigate the influence on single-mode emission. Because proton-implantation provides weak transverse confinement in the form of thermal lensing, selective loss is not required to suppress lasing of extended photonic crystal modes. We show that etching the photonic crystals to shallow depths provides the ability to scale to large aperture sizes, while etching deeply allows single-mode emission of small diameter devices. Optimized designs exhibit a net reduction in loss relative to unetched control devices, as evidenced by a reduction in device threshold current.

Wavelength-dispersive device based on a Fourier-transform Michelson-type arrayed waveguide grating

We propose a new type of arrayed waveguide grating (AWG) device that operates as a Fourier-transform (FT) spectrometer without the need of scanning elements. The large input aperture size typical of a FT spectrometer eliminates the requirement for a narrow single-mode input waveguide while still achieving high spectral resolution with a markedly increased light-gathering capability (etendue). An example of the device with a resolution of 0.07 nm (approximately 10 GHz) and designed for a silicon-on-insulator platform is presented. The calculated spectra show no noticeable deterioration for aperture widths as large as 40 microm, yielding more than a 50-fold increase in aperture size compared with conventional AWG or echelle grating based devices at the equivalent resolution.

Far-infrared detection limits - I. Sky confusion due to Galactic cirrus

Fluctuations in the brightness of the background radiation can lead to confusion with real point sources. This type of confusion with background emission is relevant when making infrared (IR) observations with relatively large beam sizes, since the amount of fluctuation tends to increase with the angular scale. To quantitively assess the effect of the background emission on the detection of point sources for current and future far-IR observations by space-borne missions such as Spitzer, ASTRO-F, Herschel and Space Infrared Telescope for Cosmology and Astrophysics (SPICA), we have extended the Galactic emission map to a higher level of angular resolution than that of the currently available data. Using this high-resolution map, we estimate the sky confusion noise owing to the emission from interstellar dust clouds or cirrus, based on fluctuation analysis and detailed photometry over realistically simulated images. We find that the confusion noise derived by simple fluctuation analysis agrees well with the results from realistic simulations. Although sky confusion noise becomes dominant in long wavelength bands (>100 µm) with 60‐90 cm aperture missions, it is expected to be two orders of magnitude lower for the next generation of space missions (with larger aperture sizes) such as Herschel and SPICA.

Apical Diffusion of Calcium Hydroxide in an in vitro Model

An in vitro agar model was developed to study the effect of intracanal medicaments on periapical tissues and was used to study the diffusion of three calcium hydroxide (Ca(OH)2) medicaments of varying viscosity through simulated root canals with various sizes of apical foramina. Experimental medicaments were added to pipette tips used to represent tooth roots, which were fixed in syringes containing brain heart infusion agar and calcium-reactive dye. OH and Ca concentrations were measured in the agar at 30 minutes and 24 hours. Ca concentration and pH increased with larger aperture sizes, and higher pH and Ca diffusion was produced by a 10% Ca(OH)2 solution than was produced by Pulpdent or a Ca(OH)2 paste. The results suggest that the properties of the Ca(OH)2-containing vehicle could affect the action of the medicament in the periapical tissues.