Microns Particles Research Articles

Stability-indicating HPLC method for the determination of related substances in lansoprazole sulphide

Symmetric peak shape was on a C18 stationary phase with the dimensions of 250 mm column length, 4.6 mm as internal diameter, 5 microns particles with an economical and straightforward mass-compatible mobile phase combination of formic acid and acetonitrile delivered in gradient mode at a flow rate of 1.0 mL/min at 260 nm. The resolution between Lansoprazole sulphide (LAN30) and its impurities (LAN30-I & LAN30-II) in the developed method was more than 2.0, indicating a significant separation. Regression analysis shows a correlation coefficient greater than 0.999 for Lansoprazole sulphide and its related substances. The detection limits of Lansoprazole sulphide and its impurities are 0.003%, 0.01%, and 0.01%; the quantitation limits are 0.01%, 0.03%, and 0.03% for LAN30, LAN30-I, and LAN30-II. This method indicates that the recovery at different levels is 95 to 105% accurate. The test solution was stable in the diluent for 48 h at refrigerator temperature and subjected to stress conditions. The mass balance was close to 99.5%.

STABILITY-INDICATING HPLC METHOD FOR THE DETERMINATION OF RELATED SUBSTANCES IN LANSOPRAZOLE INTERMEDIATE

A novel, reversed-phase liquid chromatographic method was developed and validated for the determination of related substances in lansoprazole intermediate. Symmetric peak shape was on a C18 stationary phase with the dimensions of 250 mm column length, 4.6 mm as internal diameter, 5 microns particles with an economical and straightforward mass-compatible mobile phase combination of formic acid/triethylamine and acetonitrile delivered in gradient mode at a flow rate of 1.0 mL/min at 260 nm. The resolution between lansoprazole intermediate (LAN20) and its impurities (LAN20-I & LAN20-II) in the developed method was more than 2.0, indicating a significant separation. Regression analysis shows a correlation coefficient greater than 0.999 for lansoprazole intermediate and its related substances. The detection and quantitation limits of lansoprazole intermediate and its impurities are 0.01% and 0.005%. This method indicates that the recovery at different levels is 90 to 110% accurate. The test solution was stable in the diluent for 48 h and subjected to stress conditions. The mass balance was close to 99.5%.

Training Manual for Prevention of Covid-19 Disease among Hospital Personnel

Training Manual for Prevention of Covid-19 Disease among Hospital Personnel

Planet-induced Vortices with Dust Coagulation in Protoplanetary Disks

Abstract In this work, we study how the dust coagulation/fragmentation will influence the evolution and observational appearances of vortices induced by a massive planet embedded in a low-viscosity disk by performing global 2D high-resolution hydrodynamical simulations. Within the vortex, due to its higher gas surface density and steeper pressure gradients, dust coagulation, fragmentation, and drift (to the vortex center) are all quite efficient, producing dust particles ranging from 1 μm to ∼1.0 cm, as well as an overall high dust-to-gas ratio (above unity). In addition, the dust size distribution is quite nonuniform inside the vortex, with the mass-weighted average dust size at the vortex center (∼4.0 mm) being a factor of ∼10 larger than other vortex regions. Both large (∼millimeter) and small (tens of microns) particles contribute strongly to affect the gas motion within the vortex. As such, we find that the inclusion of dust coagulation has a significant impact on the vortex lifetime and the typical vortex lifetime is about 1000 orbits. After the initial gaseous vortex is destroyed, the dust spreads into a ring with a few remaining smaller gaseous vortices with a high dust concentration and a large maximum size (∼millimeter). At late time, the synthetic dust continuum images for the coagulation case show as a ring inlaid with several hot spots at the 1.33 mm band, while only distinct hot spots remain at 7.0 mm.

DEVELOPMENT OF ORE-THERMAL MELTING TECHNOLOGY FOR AGGLOMERATED CHARGE CONTAINING TECHNOGENIC RAW MATERIAL IN SILICON PRODUCTION

Production of silicon in ore-thermal furnaces (OTF) by carbothermic reduction of quartzites is accompanied by large dust emission, containing significant amount of valuable silica (an average of 86 %). In this regard, works devoted to raw material base expansion due to return of technogenic wastes into technological process are of great significance. To be used in process of silicon smelting in OTF, the dust collected by gas treatment units, consisting of 120 microns particles with predominant fraction of +20 – 50 μm, has to pass through preliminary agglomeration (to prevent its possible fly from reaction zone with process gases). Since charge including agglomerated part must have sufficient strength during transportation and loading to OTF, liquid glass is suggested to be used as a binder with addition of aluminum-containing electrostatic precipitators containing resinous substances (polyaromatic hydrocarbons) as a hardening reagent for dust. Based on the results of tests for strength of the agglomerated charge samples, the following charge components ratio is recommended: 24 – 27 % of silicon production dust; 51 – 53 % of carbonaceous reductant (1:1 mixture of petroleum coke and charcoal); 4 – 5 % oversize of fine-grained silicon; 14 – 15 % of binder (liquid glass and dust of electrostatic precipitators of aluminum-magnesium production in 4:1 ratio) (by weight). With such a composition of charge, the drop resistance coefficient averaged 82.5 %. As a result of physical-chemical study of agglomerated compositions obtained by the proposed method, it was found that they have porous structure (45.5 %) which forms a well-developed active surface of material with an apparent density (1100 kg/cm3), which provides operation of OTF in a stable mode when using agglomerated charge of this composition. Experimental melting carried out in a HTF 17/10 type high-temperature furnace has resulted in a product containing more than 44 % (by weight) of silicon carbide as an obligatory intermediate in carbothermic process, that allows to recommend charge agglomerated by proposed procedure with selected component ratio for use as additives to the main (cobbed) charge in production of silicon by carbothermic method.

The effect of multiple particle sizes on cooling rates of chondrules produced in large‐scale shocks in the solar nebula

AbstractChondrules represent one of the best probes of the physical conditions and processes acting in the early solar nebula. Proposed chondrule formation models are assessed based on their ability to match the meteoritic evidence, especially experimental constraints on their thermal histories. The model most consistent with chondrule thermal histories is passage through shock waves in the solar nebula. Existing models of heating by shocks generally yield a good first‐order approximation to inferred chondrule cooling rates. However, they predict prolonged heating in the preshock region, which would cause volatile loss and isotopic fractionation, which are not observed. These models have typically included particles of a single (large) size, i.e., chondrule precursors, or at most, large particles accompanied by micron‐sized grains. The size distribution of solids present during chondrule formation controls the opacity of the affected region, and significantly affects the thermal histories of chondrules. Micron‐sized grains evaporate too quickly to prevent excessive heating of chondrule precursors. However, isolated grains in chondrule‐forming regions would rapidly coagulate into fractal aggregates. Preshock heating by infrared radiation from the shock front would cause these aggregates to melt and collapse into intermediate‐sized (tens of microns) particles. We show that inclusion of such particles yields chondrule cooling rates consistent with petrologic and isotopic constraints.

Analysis of dust removal equipment used in the manufacture of soluble powders

Analyzed the system of drying plant air cleaning, specializing in the production of food powders, dust emission identified place in the shop drying in the production of soluble dietary powders, the parameters of the dryer exhaust coolant, analyzed the properties of the product, as well as determined the effectiveness of the use of air purification equipment. Analyzed used at the enterprise two-stage cleaning system. As a first purification stage conical cyclone installed as a second stage purification analyzed dust collector is proposed with internal circulation of the liquid. It was found that the drying of the powder contained in the emissions of a large proportion of the fine fraction of dust. Several studies have been conducted with this food dust. It was found that the collection efficiency in the cyclone ranged from 68% (tea dust) to 92% (dust kvass wort). Analyzing the data obtained indicated that the efficiency of cleaning exhaust coolant is heavily dependent on the food composition of disperse dust, and less than 10 microns particles is insufficient. It is proposed to use for cleaning the coolant wet dust collector with internal circulation of the liquid. The regularities of change of concentration of solids in the cleaning liquid, its viscosity and surface tension with increasing operating time since the start of the dust collector. It is found that increasing the concentration of solids in the cleaning liquid increases with the operating time of the machine since the start-up leads to changes in surface tension and viscosity of the liquid. It is shown that the effective dust collection in the machine decreases as the viscosity of the working fluid. Both theoretically and experimentally established patterns may be used when calculating the optimum specific liquid flow to provide effective cleaning and releases the trapped product return process cycle.

Structure-mechanical model for plasto-elastic behavior of soft magnetic elastomers

The effect of field-induced plasticity (magnetic shape memory) displayed by polymer composites filled with multi-domain ferromagnetic microparticles is discussed. Such a soft magnetic elastomer (SME) magnetizes, that is, the filler particles acquire magnetic moments only upon application of an external magnetic field. ‘Switching-on’ of interparticle magnetic interactions essentially affects the internal structure of SMEs since the magnetic forces by far exceed the high-elasticity ones due to attachment of the particles to the polymer matrix. According to the hypothesis, in a SME there self-organizes a network of clusters that gives birth to the effect of internal dry friction and by that imparts plasticity to the composite. Field-induced structuring, together with plasticity, disappears as soon as the external field is turned off. Under these conditions, elastic forces no longer experience any resistance and move the particles back to their initial spatial positions: the sample ‘recalls’ its initial shape. To account for the above-described plasto-elastic behavior of a magnetized SME, a structure-mechanical model (scheme) is proposed, which comprises the elastic elements (springs) and the entities (Saint-Venant elements) mimicking the dry-friction effect. The elements of the model are heuristically identified with two networks. One of them is related to the polymer matrix as itself, while another resembles the particle clusters formed due to the field-induced magnetic interactions. Both networks are interwoven and may deform only affinely. On the basis of the model, the tensile deformation cycles obtained in experiments on the two types of SMEs made of weakly-linked silicone rubber filled with carbonyl iron microparticles are interpreted. The tested SMEs differ by the dispersity of the filler. The samples of the first type contain only ‘fine’ iron particles with the size of 2-5 microns, while in the SME of the second type the filler consists of equal (by weight) amounts of ‘fine’ and ‘coarse’ (~70 microns) particles. The cycles measured under a number of external fields are presented. By fitting experimental data, the parameters of the theoretical scheme are evaluated, and their dependence on the applied field strength is determined. For the field dependencies of the scheme parameters of the isotropic SMEs examined here, the expressions borrowed from the phenomenology of textured SMEs are taken and tested, proving their applicability for this case.

Efficiency in supercritical fluid chromatography with different superficially porous and fully porous particles ODS bonded phases

The chromatographic efficiency, in terms of plate number per second, was dramatically improved by the introduction of sub-two microns particles with ultra-high pressure liquid chromatography (UHPLC). On the other hand, the recent development of superficially porous particles, called core–shell or fused-core particles, appears to allow the achievement of the same efficiency performances at higher speed without high pressure drops. CO2-based mobile phases exhibiting much lower viscosities than aqueous based mobile phases allow better theoretical efficiencies, even with 3–5μm particles, but with relative low pressure drops. They also allow much higher flow rates or much longer columns while using conventional instruments capable to operate below 400bar. Moreover, the use of superficially porous particles in SFC could enhance the chromatographic performances even more. The kinetic behavior of ODS phases bonded on these particles was studied, with varied flow rates, outlet (and obviously inlet) pressures, temperatures, by using a homologous series (alkylbenzenes) with 10% modifier (methanol or acetonitrile) in the carbon dioxide mobile phase. Results were also compared with classical fully porous particles, having different sizes, from 2.5 to 5μm. Superior efficiency (N) and reduced h were obtained with these new ODS-bonded particles in regards to classical ones, showing their great interest for use in SFC. However, surprising behavior were noticed, i.e. the increase of the theoretical plate number vs. the increase of the chain length of the compounds. This behavior, opposite to the one classically reported vs. the retention factor, was not depending on the outlet pressure, but on the flow rate and the temperature changes. The lower radial trans-column diffusion on this particle types could explain these results. This diffusion reduction with these ODS-bonded superficially porous particles seems to decrease with the increase of the residence time of compounds.

SIMULTANEOUS ESTIMATION OF PIOGLITAZONE, GLIMEPIRIDE AND GLIMEPIRIDE IMPURITIES IN COMBINATION DRUG PRODUCT BY A VALIDATED STABILITY- INDICATING RP-HPLC METHOD

A new, single, stability indicating RP-HPLC method has been developed and validated for the simultaneous estimation of pioglitazone, glimepiride and glimepiride impurities i.e., related compound B and related compound C from combination drug product containing pioglitazone, glimepiride and metformin HCl. The chromatographic separation was achieved on a cyano stationary phase (250 x 4.6mm, 5.0 microns particles) with simple mobile phase combination delivered in gradient mode at a flow rate of 0.8mL min -1 at 230nm. In the developed method, the critical close eluting compound of glimepiride related compound B and related compound C was found more than 6.5 resolutions. This method is capable to detect glimepiride related compound B and related compound C at a level below 0.005% with respect to glimepiride sample concentration of 0.1mg mL-1 for a 25 µL injection volume. The proposed method was validated according to the ICH guidelines and proved suitable for routine and stability analysis of these drugs in pharmaceutical preparations.

The technology of butters’ enriching with carrots’ powder

The article shows the necessity of the development the technology of butter's enrichment with carrot powder. Technological operations are given and modes of enriched butter production are established. It is suggested to use a carrot powder additives produced by convective and cold spray drying for enrichment. The images of microstructure of aqueous solutions of selected powders are given in the article. It is established that only the suspension of the powder of cold spray drying contains particles of 20-80 microns large and particles of 1-5 microns. It is also indicated that they participate in the formation of structure between powder parts. The structure between the additive's particles (convective drying) is formed slightly. Butter enriched with carrot powder was investigated. It was established that introduction of additives improves the organoleptic properties of enriched butter and simultaneously improves the performance of the structure and consistency. It was suggested that due to the introduction of powder in butter the extra space is formed between additive and butter particles. This increases the hardness of the butter and improves its heat resistance and plasticity. This assumption is consistent and is supported by studies of additives’ microstructure. It is set that the powders obtained by different drying technologies influence differently the structures’ formation of enriched butter. A products’ fat phase was studied by differential scanning calorimetry. By diffraction pattern it was found that introducing carrots powder impedes recrystallization of glycerides during the enriched butter storage. It is set, that additive's introduction and the way of their obtainment differently influence the crystallization process in enriched butter.

Development and Validation of a New Analytical Method for the Determination of Related Components and Assay of Ranolazine in Bulk Drug and Pharmaceutical Dosage Forms by LC

A novel liquid chromatographic method has been developed and validated for the determination of ranolazine, its potential four impurities in drug substance and drug products. Efficient chromatographic separation was achieved on a C18 stationary phase (150 × 4.6 mm, 3.0 microns particles) with simple mobile phase combination delivered in gradient mode at a flow rate of 1.0 mL min−1 at 210 nm. In the developed method, the resolution between ranolazine and its four potential impurities was found to be greater than 2.0. Regression analysis shows an r value (correlation coefficient) greater than 0.999 for ranolazine and for its four impurities. This method was capable to detect all four impurities of ranolazine at a level below 0.004% with respect to test concentration of 1.0 mg mL−1 for a 10 μL injection volume. The method has shown good, consistent recoveries for ranolazine (98.8–101.1%) and for its four impurities (97.2–100.3). The test solution was found to be stable in the diluent for 48 h. The drug was subjected to stress conditions. The mass balance was found close to 99.5%.

Abstract No. 378 EE: Direct Hepatic Artery Puncture for Transarterial Therapy in Liver Cancer

To describe the novel technique of direct percutaneous hepatic arterial puncture under ultrasound guidance as an alternative method to obtain intrahepatic arterial access in order to successfully perform two Yttrium-90 (Y90) radioembolization procedures and one transarterial embolization (TAE) procedure. Three patients with unresectable liver cancers who presented for transarterial therapy all demonstrated challenging vascular anatomy on pretreatment planning secondary to previous catheter-induced vessel injury and inherently complicated anatomic variations. These limitations prevented conventional transfemoral catheterization for the angiographic evaluation of the target lesion, assessment of surrounding vasculature, and ultimate delivery of the therapeutic agent. Ultrasound guidance was provided for direct percutaneous hepatic arterial puncture in order to gain alternative intrahepatic arterial access. When angiographic challenges prevent standard hepatic vascular access, the resources available to the interventional radiologist may allow for improvised delivery of various embolic particles via direct percutaneous hepatic arterial puncture under ultrasound guidance. The most technically difficult aspect of the procedure is the actual direct transhepatic puncture of the desired hepatic artery. The target vessel will be predominantly dictated by the patient's anatomy. The actual delivery of the radioembolic particles (Y90) via the direct percutaneous hepatic arterial system is identical to conventional transarterial delivery, except performed in a retrograde manner. Since the tip of the catheter is directed centrally, the microspheres are deposited proximally which allows natural flow dynamics to carry the particles distally (antegrade) to the tumor bed. Spherical (150-300 microns) particles were infused in the bland embolization case. The vascular anatomy and the location of the target lesion in the right liver lobe allowed for antegrade catheterization of the supplying hepatic arterial branch. The delivery of the particles was identical to conventional bland embolization and was performed until flow stagnation was achieved.

Initial Permeability of Magnetically Soft Particles with Composite Structure

Fine-particle composites consisting of high-permeability particles with a large size difference exhibit enhanced initial permeability. From an analysis of the initial permeability of a composite that includes Fe (1 micron) particles as a main component, we found that the microscopic demagnetizing field imposed on the particles is appreciably reduced, allowing enhancement of the initial permeability up to the intrinsic permeability of Fe particles. The significance of this effect is exemplified using composites that include Ni50Fe50 (6 microns) and amorphous Fe-Si-B-Cr (3 microns) particles. According to a calculation of the eddy current in spheres with high permeability, reduction of the particle size to less than 1 micron is essential for further improvement of the high-frequency performance of particle composites.

Design of Some Oxide/Metal Composite Supports and Catalysts

Textural, mechanical and catalytic properties of porous composite materials Al2O3/Al, MeO x (Me)/Al2O3/Al with metal particles homogeneously distributed in the alumina matrix were studied. These materials were prepared by mixing the powdered components with aluminum followed by hydrothermal treatment and calcination. The macroporous structure was shown to be controlled by the size of large (>microns) particles in starting blends. The mesoporous structure is primarily determined by the properties of alumina formed by dehydration of hydroxide produced in turn via aluminum oxidation by water. The mechanical strength of porous cermets is determined by the number and properties of contacts between micron-size components of composites. Improved catalytic performance of composites is ensured by the developed macroporous structure providing enhanced mass transfer inside the cermet granules.

Fast RPLC-UV method on short sub-two microns particles packed column for the assay of tenoxicam in plasma samples

An extraction-less sample preparation technique followed by a RPLC-UV method on sub-two microns particles packed short column were used for the assay of tenoxicam in plasma samples. Protein precipitation was made by means of trichloroacetic acid addition. Supernatant was injected to the chromatographic column without any further pH adjustment. The mobile phase consisted in a mixture of acetonitrile and aqueous 0.1% phosphoric acid, at 2 mL/min flow rate and gradient elution. The Zorbax SB-C18 ® column (50 mm length, 4.6 mm internal diameter and 1.8 μm particle size) was thermostated at 60 °C. The mobile phase gradient composition program allowed separation of tenoxicam and piroxicam (internal standard), column clean-up and re-equilibration within 4 min. UV detection was achieved at 368 ± 10 nm. The method is characterized by a low limit of quantitation of 25 ng/mL for tenoxicam, with a linearity interval up to 5500 ng/mL. The use of a low volume detection cell and detector high frequency data acquisition rate produced high precision and accuracy through a whole bioequivalence study of tenoxicam in two commercially available tablet formulations, after a single oral administration dose. Full method validation is presented. The high throughput characteristic of the proposed method allowed full validation and bioanalytical study completion within a 96 h period.

Experimental study of the sampling artifact of chloride depletion from collected sea salt aerosols.

Sampling artifact of chloride depletion from collected sea salt particles was studied, based on simultaneous measurements of size distribution measurements by a 10-stage Micro-Orifice Uniform Deposit Impactor (MOUDI) and of PM2.5 measurements by a Compact Porous Metal Denuder Sampler (PMDS) at a coastal site in Hong Kong on May 7, 8, 9, 11, and 29, 1998. The ambient concentrations of SO2, HNO3, HNO2, and NH3 were also measured by the PMDS. PM2.5 measurements by the PMDS, which is equipped with denuders and nylon back filters, are compared with the PM1.8 and PM3.1 measurements by the MOUDI. The percentages of chloride depletion from sea salt aerosols in PM1.8 and PM3.1 were 4-45% higher than that in PM2.5. This suggests that chloride evaporation in PM1.8 and PM3.1 collected on Teflon filters of the MOUDI during sampling was present. From the sum of the contributions of particles on the Teflon and nylon filters of the PMDS, nitrate formation almost completely accounts for chloride depletion in PM2.5 prior to collection since the equivalent ratio of [Na+] to ([NO3-] + [Cl-]) is close to the seawater ratio of 0.85. However, it was found that 22-74% of nitrate and 45-86% of chloride in the collected particles on the Teflon filter of the PMDS evaporated during sampling. Excess chloride depletion unexplained by NO3- and nss-SO4(2-) was found in the collected particles on the Teflon filter of the PMDS. Similarly, an amount of 3.7-27.2 nequiv m-3 of excess depleted chloride (equivalent to 8-55% of total chloride depletion) was found in supermicron particles collected by the MOUDI. In the 1.8-3.1 microns particles, the excess depleted chloride is positively correlated to the chloride evaporated from the deposited particles. Particle--particle interactions are proposed to explain the evaporation of nitrates and chlorides in the PMDS and MOUDI measurements. The observed chloride depletion from seasalt aerosols was partially attributed to sampling artifact due to particle--particle interactions.

Effects of titanium surfaces blasted with TiO2 particles on the initial attachment of cells derived from human mandibular bone

This study was performed to determine the effect of commercially pure titanium surfaces blasted with TiO2 particles on the biological responses of cells derived from human mandibular bone. The morphology and attachment of those cells were investigated on turned titanium surfaces (control) and surfaces blasted with 45 microns (standard), 45-63 microns, and 63-90 microns TiO2 particles. The surfaces were analyzed in a scanning electron microscope. Based on surface analyses reported elsewhere, the turned samples had the smoothest surfaces and the roughest were those blasted with the largest particles (63-90 microns). The cell profile areas were measured using a semi-automatic interactive image analyzer. The attachment was determined as a ratio of the area of cell profiles and the total micrograph area and was expressed as percentage of attachment. Morphologically, the cells were heterogeneous. In general, the cells had spread well on all titanium surfaces, indicating good attachment to both smooth and rough surfaces. After 1, 3 and 6 h, the percentage of cell attachment did not differ significantly between the surfaces blasted with 63-90 microns and the turned surfaces, but was significantly lower on the surfaces blasted with 45 microns or 45-63 microns particles. After 24 h the surfaces blasted with 63-90 microns particles had a higher rate of cell attachment than all the other surfaces including the controls. It is concluded that attachment and growth of cells originating from human mandibular bone in vitro, are influenced by the micro-texture of the implant surface.

Attachment and proliferation of human oral fibroblasts to titanium surfaces blasted with TiO2 particles. A scanning electron microscopic and histomorphometric analysis.

The purpose of this study was to determine the effect of c.p. titanium surfaces blasted with TiO2 particles on the biological responses of human gingival fibroblasts (HGF). Fibroblast morphology and attachment were investigated on turned (control) titanium surfaces and those blasted with 45 microns (standard), 45-63 microns, and 63-90 microns TiO2 particles. The specimens were analyzed using a confocal laser scanner and SEM. The cell profile areas were measured using a semiautomatic interactive image analyser. The figures were expressed as percent of attachment. The turned samples had the smoothest surfaces and the roughest were those blasted with 63-90 microns. All TiO2 blasted specimens had homogeneous surfaces. Cells appeared to flatten, spread and form cellular bridges with the adjacent cells. Fibroblasts on the turned titanium surfaces appeared to follow the direction of the fine irregularities on the surface but tended to spread haphazardly on the blasted surfaces. The attachment assays showed no significant difference in the percentage of fibroblast cell attachment on the standard surfaces compared to the turned surfaces. Both surfaces blasted with 45-63 microns or 63-90 microns had significantly (P < 0.05) lower percentages of cell attachment than the control. The surfaces blasted with 63-90 microns particles had the lowest rate of cell attachment. A significant correlation (P < 0.01) was found between the degree of particle size and attachment of fibroblasts after 1-72 h. It is concluded that surface micro-texture influences the attachment and growth of HGF: surfaces blasted with 45 microns TiO2 do not inhibit fibroblast attachment and smooth or finely grooved surfaces could be conducive to cellular attachment.

An analytical framework for relating dose, risk, and incidence: an application to occupational tuberculosis infection.

An adverse health impact is often treated as a binary variable (response vs. no response), in which case the risk of response is defined as a monotonically increasing function R of the dose received D. For a population of size N, specifying the forms of R(D) and of the probability density function (pdf) for D allows determination of the pdf for risk, and computation of the mean and variance of the distribution of incidence, where the latter parameters are denoted E[SN] and Var[SN], respectively. The distribution of SN describes uncertainty in the future incidence value. Given variability in dose (and risk) among population members, the distribution of incidence is Poisson-binomial. However, depending on the value of E[SN], the distribution of incidence is adequately approximated by a Poisson distribution with parameter mu = E[SN], or by a normal distribution with mean and variance equal to E[SN] and Var[SN]. The general analytical framework is applied to occupational infection by Mycobacterium tuberculosis (M. tb). Tuberculosis is transmitted by inhalation of 1-5 microns particles carrying viable M. tb bacilli. Infection risk has traditionally been modeled by the expression: R(D) = 1 - exp(-D), where D is the expected number of bacilli that deposit in the pulmonary region. This model assumes that the infectious dose is one bacillus. The beta pdf and the gamma pdf are shown to be reasonable and especially convenient forms for modeling the distribution of the expected cumulative dose across a large healthcare worker cohort. Use of the the analytical framework is illustrated by estimating the efficacy of different respiratory protective devices in reducing healthcare worker infection risk.