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PubMed2006

Technique for routine output verification of Leipzig applicators with a well chamber.

The H-type Leipzig applicators are accessories of the microSelectron-HDR system (Nucletron, Veenendaal, The Netherlands) for treatment of superficial malignancies. Recently, the dose rate distributions in liquid water for the whole set of applicators using both source models available for the microSelectron-HDR afterloaders have been obtained by means of the experimentally validated Monte Carlo (MC) code GEANT4. Also an output table (cGy/hU) at 3 mm depth on the applicator central axis was provided. The output verification of these applicators by the user, prior to their clinical use, present practical problems: small detectors such as thermoluminescent dosimeters or parallel-plate ionization chambers are not easily used for verification in a clinical environment as they require a rigid setup with the Leipzig applicator and a phantom. In contrast, well-type ionization chambers are readily available in radiotherapy departments. This study presents a technique based on the HDR1000Plus well chamber (Standar Imaging) measurements with a special insert, which allows the output verification of the H-type Leipzig applicators on a routine basis. This technique defines correspondence factors (CF) between the in water dose rate output of the Leipzig applicators (cGy/hU) obtained with MC and the reading on the well chamber with the special insert, normalized to the HDR calibration factor with the HDR insert and to the source strength. To commission the applicators (with the well chamber and the special insert used), the physicist should check if the CF value agrees with its tabulated values presented in this work. If the differences are within 5% the tabulated output values can be used in clinical dosimetry. This technique allows the output validation of the Leipzig applicators with a well chamber widely used for HDR Ir-192 source strength measurements. It can easily be adapted to other types of well chambers for HDR source output verification.

Brachytherapy↗

PubMed1995

Major geometric variations between multiple high-dose-rate applications of brachytherapy in cancer of the cervix: frequency and types of variation.

PURPOSE: To evaluate major geometric variations in multiple intracavitary applications for carcinoma of the cervix. MATERIALS AND METHODS: Orthogonal radiographs were reviewed of 17 consecutive patients with carcinoma of the cervix treated with 70 applications of high-dose-rate brachytherapy. In seven patients, conscious sedation was used for all applications. In 10 patients, general anesthesia was used for the first application and conscious sedation for subsequent applications. Major geometric variation between applications in axis, length, and slippage in tandem placement and separation, packing, and slippage in colpostats placement were reviewed. A major variation was defined as more than 1.0-cm deviation. RESULTS: Major variations between applications occurred more commonly in colpostats placement than in tandem placement. For tandems, the rates of variation were 5.7% in axis, 4.3% in length, and 1.4% in slippage. For colpostats, rates of variation were 7.1% in separation, 25.7% in vaginal packing, and 7.1% in slippage. No consistent pattern of variation was found between applications except in vaginal packing. CONCLUSION: Awareness of geometric variations should improve proper placement of intracavitary applicators for brachytherapy.

Anesthesia, General↗

PubMed1989

Consequences of 4-aminopyridine applications to trigeminal root ganglion neurons.

1. The effects of 4-aminopyridine (4-AP) on the electrical properties of 30 trigeminal root ganglion (TRG) neurons were determined from the membrane voltage responses to step and sinusoidal current injections using intracellular microelectrode techniques in in vitro slice preparations (guinea pigs). 2. Comparisons of results from 4-AP applications (0.05-5 mM) with those from tetraethylammonium (TEA) applications (0.1-10 mM) revealed very different actions of these agents. Both agents produced an increase in input resistance and a decrease in threshold for spike generation. Applications of 4-AP increased subthreshold oscillations of the membrane potential and enhanced the repetitive spike firing evoked by intracellular injections of current pulses. However, TEA applications blocked the potential oscillations and did not exaggerate repetitive spike discharges. Spontaneous spike activity or bursts were observed in four neurons that received 4-AP applications. 3. Membrane properties were determined in 20 of the 30 neurons by fitting impedance data in the frequency domain with a four-parameter membrane model by the use of computer-intensive techniques. In the majority of neurons, the time-invariant and time-dependent membrane conductances decreased during 4-AP application. The time constant for the time-dependent conductance also decreased, suggesting that the closing of K+-channels was facilitated in the membrane. 4. Applications of 4-AP in a dose range of 50 microM-5 mM produced rapid (approximately tens of seconds) responses of the neurons, resulting in a dose-dependent increase of the impedance magnitude functions and in a leftward shift of the resonant "humps" to lower frequencies. This shift indicates that the TRG neuronal membrane is capable of producing large voltage responses to current inputs at low frequencies. Recovery from the effects of 4-AP was slow (usually greater than 30 min). 5. Applications of 4-AP at high doses (greater than or equal to 1 mM) and at various imposed membrane potentials in four neurons resulted in poorly reversible unspecific changes in certain membrane parameters (increased input capacitance and conductance) and an insensitivity of the input conductance to the imposed membrane potential. These effects could be interpreted as membrane breakdown. 6. The tendencies of TRG neurons to fire repetitively and in bursts of spikes during 4-AP application result from the increased oscillatory behavior of their membrane potentials and changes in membrane resonance induced by presumed blockade of K+ channels.(ABSTRACT TRUNCATED AT 400 WORDS)

4-Aminopyridine↗

PubMed2002

[Cerebral hemodynamics in carbon dioxide applications].

INTRODUCTION: We compare the effect of carbon dioxide (CO(2)) dry and wet applications on cerebral hemodynamics. METHODS: On 22 volunteers measurements were taken during CO(2) application. 10 probands were examined in CO(2) wet application (1,100-1,300 mg/l) and 12 probands in CO(2) dry application (500 g in a 800 l bathtub). The cerebral blood flow velocity (CBFV) in the middle cerebri artery (MCA) was measured as a parameter of cerebral hemodynamics by means of transcranial doppler sonography. Furthermore were recorded CO(2) expiratory concentration (CO(2)et), blood pressure, and sublingual temperature. RESULTS: At CO(2) wet application the CBFV increased during therapy phase by 15% (p = 0.001), parallel to the rise of the CO(2)et by 18% (p = 0.01). During CO(2) dry application CBFV decreased by 11% (p = 0.007), body temperature increased significantly by 0.2 degrees C. CONCLUSION: CO(2) applications have influence on cerebral hemodynamics. Assuming constant diameters of the great brain vessels, CO(2) wet application shows a raising and CO(2) dry application a reducing influence on cerebral blood flow. This influence will attain therapeutic relevance.

Blood Flow Velocity↗

PubMed2005

Update on personal digital assistant applications for the healthcare provider.

OBJECTIVE: To review the common general drug information applications and specialty drug information applications available for personal digital assistants (PDAs). DATA SOURCES: The literature was accessed through MEDLINE (2003-June 2004). Other information was obtained through secondary sources, such as Web sites describing common PDA applications as well as actual product trials. The key search terms used were handheld, PDA, personal digital assistants, drug information, pharmacokinetics, medical information, and medical applications. STUDY SELECTION AND DATA EXTRACTION: Articles or studies that provided a review of drug information references for the PDA since 2002 were included. Data pertaining to cost and application size were obtained from product or vendor Web sites. DATA SYNTHESIS: There are numerous medical applications available for the PDA including general drug information references, specialty drug information references (eg, pediatrics, cardiology, infectious diseases, oncology, psychology, herbals), diagnostic applications, medical calculators, nursing references, and patient tracking databases. Due to the huge array of programs, as well as factors such as cost and memory requirements, the healthcare provider must be selective in the medical applications that are placed on the PDA. CONCLUSIONS: There are many excellent PDA drug information applications that provide fast and accurate drug information and other features that assist the healthcare provider.

Adult↗

PubMed1994

A new capacitive heating applicator for the simultaneous radiohyperthermotherapy of superficial and shallow-seated tumors.

External capacitive heating is the usual method of electromagnetic wave heating, in which the tumor is caught and heated between two opposite applicators. Using a phantom, the authors developed and evaluated the performance of a new capacitive heating applicator designed for simultaneous radiohyperthermotherapy (SRH) in which the electron beam irradiation is provided from above an external capacitive heating applicator for the treatment of superficial and shallow-seated tumors. The trial applicator was constructed to fulfill the following conditions: 1. use of an electrode plate which does not affect the electron beam depth dose, 2. a uniform thickness to maintain flatness of the electron beam, and 3. a cooling function to prevent damage to normal skin tissue and enhance the therapeutic gain factor. This applicator was comprised of a 0.1-mm-thick copper electrode and a 5-mm-thick cooling chamber. The depth of the 80% dose of the new applicator was 21 mm with a 9-MeV electron beam and 36mm with a 15-MeV electron beam, which was comparable to the effect of a conventional irradiation bolus. The temperature distribution produced by the trial applicator was symmetrical on both sides from the center of the applicator. The 50% specific absorption rate region was 6.4 cm wide at a depth of 1 cm from the phantom surface and 2.8 cm wide at a depth of 3 cm. There have been no previous reports on the development of an external capacitive heating applicator designed for the SRH of superficial and shallow-seated tumors; this is the first such report.(ABSTRACT TRUNCATED AT 250 WORDS)

Combined Modality Therapy↗

PubMed1990

Potential exposure and health risks of infants following indoor residential pesticide applications.

Air and surface chlorpyrifos residues were measured for 24 hours following a 0.5 percent Dursban broadcast application for fleas inside a residence. Two of the three treated rooms were ventilated following application. Maximum air concentrations were measured 3-7 hours post-application. Peak concentrations in the infant breathing zone were 94 micrograms/m3 in the nonventilated room and 61 micrograms/m3 in the ventilated room, and were substantially higher than concentrations in the sitting adult breathing zone. Concentrations of approximately 30 micrograms/m3 were detected in the infant breathing zone 24 hours post-application. Surface residues available through wipe sampling were 0.7-1.6 micrograms/cm2 of carpet on the day of application and 0.3-0.5 micrograms/cm2 24 hours post-application. Estimated total absorbed doses for infants were 0.08-0.16 mg/kg on the day of application and 0.04-0.06 mg/kg the day following application, with dermal absorption representing approximately 68 percent of the totals. These doses are 1.2-5.2 times the human No Observable Effect Level (NOEL). Exposures to cholinesterase inhibiting compounds following properly conducted broadcast applications could result in doses at or above the threshold of toxicological response in infants, and should be minimized through appropriate regulatory policy and public education.

Air Pollutants↗

PubMed2004

The relationship between required medical school instruction in musculoskeletal medicine and application rates to orthopaedic surgery residency programs.

BACKGROUND: Orthopaedic residency programs lack gender and race diversity. This study examines the hypothesis that exposure to a required course in musculoskeletal medicine in medical school is associated with a higher rate of application to orthopaedic surgery residency programs by underrepresented groups. METHODS: All 122 medical schools in the United States were surveyed in 2001 to determine whether they required dedicated course work in musculoskeletal medicine, defined as a preclinical module or clinical clerkship in orthopaedic surgery, rheumatology, or physiatry. Data from the Electronic Residency Application Service were obtained for the class of 2002. From these two sources, the rate of applications from students to orthopaedic surgery residency programs was calculated as a function of exposure to a required course in musculoskeletal medicine. Subgroup analysis was further carried out for women and for African Americans, Latinos, and Native Americans. RESULTS: In 2002, there were 16,294 graduates of American medical schools, of whom approximately 55% had mandatory instruction in musculoskeletal medicine. The rate of application to orthopaedic surgery residency programs was 5.7% among the students with required instruction compared with a rate of 5.1% for students without such required instruction. The rate of application for female students was 2.0% for those who had required courses and 1.1% for the female students who had not had the required courses. The rate of application for minority students in schools with required courses was 8.2% compared with a rate of 6.1% for those students without such exposure. CONCLUSIONS: Required instruction in musculoskeletal medicine was associated with a 12% higher rate of application to orthopaedic surgery residency programs among all students (5.7% of those who received required instruction compared with 5.1% of those who did not). The relative difference was more pronounced among women (a 75% difference in the rate of application) and minorities (a 35% difference in the rate of application). This study suggests that required instruction in musculoskeletal medicine can help to promote diversity in orthopaedic surgery residency programs.

Cultural Diversity↗

PubMedDate not supplied

Distribution and leaching of methyl iodide in soil following emulated shank and drip application.

Methyl iodide (MeI) is a promising alternative to methyl bromide in soil fumigation. The pest-control efficacy and ground water contamination risks of MeI as a fumigant are highly related to its gas-phase distribution and leaching after soil application. In this study, the distribution and leaching of MeI in soil following shank injection and subsurface drip application were investigated. Methyl iodide (200 kg ha(-1)) was directly injected or drip-applied at a 20-cm depth into Arlington sandy loam (coarse-loamy, mixed, thermic Haplic Durixeralfs) columns (12-cm i.d., 70-cm height) tarped with virtually impermeable film. Concentration profiles of MeI in the soil air were monitored for 7 d. Methyl iodide diffused rapidly after soil application, and reached a 70-cm depth within 2 h. Relative to shank injection, drip application inhibited diffusion, resulting in significantly lower concentration profiles in the soil air. Seven days after MeI application, fumigated soil was uncapped, aerated for 7 d, and leached with water. Leaching of MeI was significant from the soil columns under both application methods, with concentrations of >10 mug L(-1) in the early leachate. The leaching was greater following shank injection than drip application, with an overall potential of 33 g ha(-1) for shank injection and 19 g ha(-1) for drip application. Persistent residues of MeI remaining in soils after leaching were 50 to 240 ng kg(-1), and the contents were slightly higher following shank injection than drip application. The results suggest that fumigation with MeI may pose a risk of ground water contamination in vulnerable areas.

Environmental Monitoring↗

PubMed2006

Outcomes of National Institutes of Health peer review of clinical grant applications.

PURPOSE: We previously reported that National Institutes of Health (NIH) peer review outcomes in 2002 were slightly but significantly less favorable for grant applications for clinical research than for laboratory research. The present analysis was undertaken to determine if factors related to the review process might contribute to this difference. METHODS: The impact of each of the following factors on median priority scores and funding rates for clinical and nonclinical R01 grant applications was evaluated: (1) the percentage of clinical applications assigned for review to a study section, (2) the requested direct costs, and (3) the clinical research experience of the reviewers. RESULTS: Confirming our previous observation, in both 1994 and 2004, median priority scores and funding rates for R01 applications were less favorable for clinical research. In 1994, clinical applications did not fare as well in study sections reviewing relatively low percentages of clinical applications. This was not the case in 2004. Although requested direct costs were greater for clinical than for nonclinical R01 applications, median priority scores within each category were actually more favorable for applications requesting greater funding. Assignment of priority scores was not different for reviewers with or without experience conducting clinical research. CONCLUSION: These data do not support the hypothesis that the less favorable review outcomes for clinical applications are related to these review factors. We suggest that peer review outcomes for clinical research will benefit from the recent refinement of NIH review criteria, emphasizing the unique contributions of clinical investigation, and from increased training opportunities for clinical investigators.

Biomedical Research↗

PubMed1999

Changes in forearm blood flow during single and intermittent cold application.

STUDY DESIGN: Two-factor repeated measures design. OBJECTIVES: To compare the effects of a 20-minute cold application to the effects of a 20-minute cold application followed by 20 additional minutes of intermittent cold on forearm blood flow over a 60-minute period. BACKGROUND: The appropriate duration of cold application as a therapeutic modality following soft tissue trauma is an important clinical question because the goal of using this modality is to limit edema, decrease pain, and produce effective muscle relaxation without causing cold-induced reactive vasodilatation or nerve damage. METHODS AND MEASURES: Thirteen subjects (mean age, 21.46 +/- 4.01 years) volunteered to participate in this study. A bilateral tetrapolar impedance plethysmograph was used with venous occlusion to measure changes in local limb blood volume at the forearm for a period of 60 minutes under 2 conditions: Condition 1: Prolonged intermittent cold application (20 minutes ice application; 10 minutes off; 10 minutes ice on; 10 minutes off; 10 minutes ice on); Condition 2: Cold followed by application of a room-temperature pack of equal weight to the ice bag (20-minute ice application; 10 minutes off; 10 minute room-temperature pack on; 10 minutes off; 10-minute room-temperature pack on). RESULTS: A significantly lower blood flow was noted during the last 10 minutes of Condition 1 compared with Condition 2. CONCLUSIONS: The findings of this study indicate that blood flow is reduced when a prolonged intermittent cold application (Condition 1) is used compared to a single cold application (Condition 2).

Adult↗

PubMedDate not supplied

Interstitial microwave hyperthermia applicators having submillimetre diameters.

Using microscopic techniques we have fabricated interstitial hyperthermia applicators having diameters of 0.20, 0.33 and 0.58 mm, which will fit through catheters of 30, 26 and 22 gauge, respectively. Existing commercial applicators having a diameter of 1.1 mm required 17 gauge (or larger) catheters. Our new applicators, which operate at 915 MHz, are a smaller version of a design used by others. We have characterized our applicators by determining the energy deposition patterns (SAR) in muscle-simulating phantoms. These patterns were determined by measuring the electric field intensity using a miniature implantable isotropic probe having a diameter of 3 mm. Contours of the SAR data for our applicators, as well as a larger commercial applicator, show that all of these applicators exhibit similar heating patterns. Test results suggest that the durability and power handling capability of our submillimetre applicators are adequate for use in patients. Our new applicators should be useful in the percutaneous treatment of deep-seated tumours, intraoperative treatments, and also permit intraluminal or intravascular access to tumours.

Biomedical Engineering↗

PubMedDate not supplied

Heating characteristics of a helical microwave applicator for transurethral hyperthermia of benign prostatic hyperplasia.

A new applicator for intraurethral hyperthermic treatment of benign prostatic hyperplasia is described. The applicator uses an insulated helical antenna wound on the outer surface of a silicone urological (Foley) balloon catheter. The balloon catheter assures rapid and reproducible localization of the antenna in the prostatic urethra. Two small cannulae are fixed to the exterior surface of the applicator. One holds a temperature control sensor at a fixed location, the other is used to map temperature along the applicator. Two-dimensional SAR and steady-state temperature distributions measured in a plane tangent to the applicator in a tissue-equivalent phantom are presented, as well as longitudinal temperature distributions measured in situ at the applicator-urethral interface. Prostatic temperatures were also measured intraoperatively. The applicator appears to be capable of elevating temperature to greater than 42 degrees C in a cylindrically symmetric volume of about 4 cm length and about 0.5 cm radial penetration surrounding the antenna. The heating characteristics of this applicator are similar to an earlier design that employed an array of three dipoles. The helical applicator is narrower, more flexible and simpler to use than the earlier design.

Biomedical Engineering↗

PubMed2002

Applicant analysis: 2000 entering class.

There were 7,770 applicants to the entering dental school class of 2000. This is almost 14 percent less than the number of applicants to the entering class of 1999. Since the peak of dental school applicants in 1997 (at 9,829), the number has declined 21 percent. (This is most similar to the decline that has occurred in medical school applicants since their peak of applicants in 1996, at 46,968.) Almost 55 percent of the applicants to dental school were enrolled in 2000. Dental schools reported 4,234 first-time, first-year enrollees in 2000. This is an increase of 25 enrollees over the number reported in 1999. Since 1989, when dental school enrollment once again began to increase, total first-year dental school enrollment has increased 8.7 percent. The number of applicants per first-time, first-year position was 1.84 in 2000. It was 2.14 in 1999. (The most recent low was 1.34 in 1989.) The GPA and DAT scores of the first-time, first-year enrollees in 2000 were all either equal to or slightly higher than they were in 1999. Women were approximately 40 percent of the applicants and first-time, first-year enrollees in 2000, up slightly from 1999. Underrepresented minorities comprised slightly over 12 percent of the applicants and 10.6 percent of the first-time, first-year enrollees, also up slightly from 1999.

Adult↗

PubMedDate not supplied

How policy variables influence the timing of applications for Social Security Disability Insurance.

This article analyzes the impact of policy variables--employer accommodations, state Social Security Disability Insurance (DI) allowance rates, and DI benefits--on the timing of an application for DI benefits by workers with a work-limiting health condition starting when their health condition first begins to bother them. The analysis uses a rich mixture of personal and employer characteristics from the Health and Retirement Study linked to Social Security administrative records. We find that most workers do not apply immediately for DI benefits when they are first bothered by a health condition. On the contrary, the median working-age man with a work-limiting condition waits 7 years after that time before applying, and the median working-age woman waits 8 years. Although the risk of applying for benefits is greatest in the year following onset, only 16 percent of men and 13 percent of women in our sample apply within the first year, and the risk of application falls thereafter. That finding suggests that institutional factors, in addition to health factors, may play a role in the timing of DI applications. Using kernel density estimates of the distribution of application and nonapplication ordered by state allowance rates (the rate of acceptance per DI determination in each state), we find that both men and women who live in states with high allowance rates are disproportionately more likely to apply for benefits in the first year after their condition begins to bother them than are those in states with low allowance rates. Using life-table analysis, we also find that men and women who are accommodated by their employers are significantly less likely to apply for DI benefits in each of the first few years after their condition begins to bother them than are those who are not accommodated. On the basis of this evidence, we include these policy variables in a model of the timing of DI application that controls for other socioeconomic variables as well as health. Using a hazard model, we find that workers who live in states with higher allowance rates apply for DI benefits significantly sooner than those living in states with lower allowance rates following the onset of a work-limiting health condition. Workers who are accommodated following the onset of a work-limiting health condition, however, are significantly slower to apply for DI benefits. Using the mean values of all explanatory variables, we estimate the relative importance of changes in these policy variables on the speed with which workers apply for benefits after onset. We find that the mean time until application for men is 10.22 years. Universal accommodations following onset would delay application by 4.36 years. In contrast, a 20 percent decrease in state allowance rates would delay application by only 0.88 years. For working-age women, the average expected time until application once a condition begins to bother them is 10.58 years. Universal accommodations would delay that by 3.76 years, and a 20 percent decrease in allowance rates would delay it by 1.47 years. A complication in this analysis is that the policy variables are to some degree endogenous. Accommodation is probably offered more often to workers who want to continue working. Allowance rates are chosen by states on the basis of federal policy and local choices and probably in part on the health condition of workers in the state. Therefore, our estimates are upper bounds of these policy effects. Still, we believe we provide evidence that the social environment faced by workers with work-limiting health conditions can significantly influence their decision to apply for DI benefits, holding their specific health conditions constant.

Adult↗

PubMedDate not supplied

Effect of manure application timing, crop, and soil type on phosphorus leaching.

Phosphorus (P) leaching losses from manure applications may be of concern when artificial drainage systems allow for hydrologic short-cuts to surface waters. This study quantified P leaching losses from liquid manure applications on two soil textural extremes, a clay loam and loamy sand soil, as affected by cropping system and timing of application. For each soil type, manure was applied at an annual rate of 93 800 L ha(-1) on replicated drained plots under maize (Zea mays L.) in early fall, late fall, early spring, and as a split application in early and late spring. Manure was applied on orchardgrass (Dactylis glomerata L.) in split applications in early fall and late spring, and early and late spring. Drain water was sampled at least weekly when lines were flowing, and outflow rate and total P content were determined. High P leaching losses were measured in the clay loam as soon as drain lines initiated flow after manure application. Flow-weighted mean P leaching losses on clay loam plots averaged 39 times higher (0.504 mg L(-1)) than those on loamy sand plots (0.013 mg L(-1)), and were above the USEPA level of concern of 0.1 mg L(-1). Phosphorus losses varied among application seasons on the clay loam soil, with highest losses generally measured for early fall applications. Phosphorus leaching patterns in clay loam showed short-term spikes and high losses were associated with high drain outflow rates, suggesting preferential flow as the main transport mechanism. Phosphorus leaching from manure applications on loamy sand soils does not pose environmental concerns as long as soil P levels remain below the saturation level.

Agriculture↗

PubMed2004

Applicants to U.S. dental schools: an analysis of the 2002 entering class.

In 2002, there were 7,537 applicants to all entering dental school classes in the United States. This represents a 1.7 percent increase over the number of applicants in 2001. Between the peak of applicants in 1997 (at 9,829) and 2001, the number declined 25.0 percent. (This is similar to the percent decline that occurred in medical school applicants since their peak in 1996, at 46,968.) Dental schools reported 4,372 first-time, first-year enrollees in 2002. This is an increase of 105 first-time, first-year enrollees over the number reported in 2001. With the 1.7 percent increase in applicants and the 2.5 percent increase in first-time, first-year enrollees over last year, 58 percent of the dental school applicants were enrolled in 2002. This is up very slightly from 57.6 percent in 2001. Since 1989 when dental school enrollment once again began to increase, the number of first-time, first-year enrollees has increased 17.7 percent. (Total first-year enrollment, which includes first-time enrollees and repeat students, has increased 11.8 percent since 1989.) The number of applicants per first-time, first-year position was 1.72 in 2002. It was 2.31 in 1997. (The most recent low was 1.34 in 1989.) The average GPA and DAT scores of first-time, first-year enrollees in 2002 were essentially unchanged from what they were in 2001. Women were 43.7 percent of the applicants and 42.7 percent of first-time, first-year enrollees in 2002, slight increases from what they were in 2001. Underrepresented minorities comprised 12.8 percent of the applicants and 11.4 percent of the first-time, first-year enrollees in 2002. These percentages are little changed from those reported in 2001.

Age Factors↗

PubMed2004

Bioaerosols from the land application of biosolids in the desert southwest USA.

This study evaluated bioaerosol emissions during land application of Class B biosolids in and around Tucson, Arizona, to aid in developing models of the fate and transport of bioaerosols generated from the land application of biosolids. Samples were collected for 20 min at distances between 2 m and 20 m downwind of point sources, using an SKC BioSampler impinger. A total of six samples were collected per sampling event, which consisted of a biosolid spray applicator applying liquid biosolids to a cotton field. Each application represented one exposure. Samples were collected in deionised water amended with peptone and antifoam agent. Ambient weather conditions were also monitored every 10 min following initiation of sampling. Concurrently with downwind samples, background (ambient) air samples were collected to compensate for any ambient airborne microorganisms. In addition, biosolids samples were collected for analysis of target indicator and pathogenic organisms. Soil samples were also collected and analysed. Significant numbers of heterotrophic plate count (HPC) bacteria were found in air samples collected during the biosolid application process. These could have arisen from soil particles being aerosolised during the land application process. Aerosolised soil may contribute significantly to the amount of aerosolised microorganisms. Soil particles may be able to more readily aerosolise, due to their low density, small particle size and low mass. Aerosolised HPC bacteria found during biosolids land application were similar to those found during normal tractor operation on non-biosolids applied fields. Coliforms and coliphages were not routinely detected even though they were found to be present in the biosolids at relatively high concentrations, 10(6) and 10(4)/g (dry weight) of biosolids respectively. This could be due to the die-off rate of aerosolised Gram-negative bacteria or sorption to the solid portion of the biosolids. Low numbers of aerosolised coliphages may likewise be due to sorption phenomena. We theorise that only organisms in the aqueous phase of the biosolids were available to desorb and be aerosolised. Animal viruses, which were not detected in the biosolids, were likewise not detected in the aerosol samples. Clostridium perfringens was detected in only a small percent of aerosol samples although it was detected during all weather conditions; other microorganisms were detected during more favourable environmental conditions (relative humidity >10%). Despite the fact that many of these organisms were present in the biosolids at significant concentrations, their presence in bioaerosols generated during the land application of biosolids was limited to only a small percentage of samples. Bacteria as well as viruses may sorb to biosolids, which contain a high percentage of organic matter, and desorption during land application of biosolids may not readily take place; therefore, these microorganisms may not be readily aerosolised.

Adsorption↗