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PubMed2003

Applicant analysis: 2001 entering class.

There were 7,412 applicants to the entering dental school class of 2001. This is 4.6 percent less than the number of applicants to the entering class of 2000. Since the peak of dental school applicants in 1997 (at 9,829), the number of applicants has declined 24.6 percent. (This decline is most similar to the 25.8 percent decline that has occurred in medical school applicants since their peak of applicants in 1996, at 46,968.) With the decline in applicants and a slight increase in first-time, first-year enrollees, 57.6 percent of the dental school applicants were enrolled in 2001. This is up from 54.5 percent in 2000. Dental schools reported 4,267 first-time, first-year enrollees in 2001. This is an increase of thirty-three first-time, first-year enrollees over the number reported in 2000 and only an increase of fifty-eight over the last two years. Since 1989, when dental school enrollment once again began to increase, the number of first-time, first-year enrollees has increased 14.9 percent. (Total first-year enrollment, which includes first-time enrollees and repeat students, has increased 10.8 percent since 1989.) The number of applicants per first-time, first-year positions was 1.74 in 2001. It was 2.31 in 1997. (The most recent low was 1.34 in 1989.) The average of the GPA and DAT scores of the first-time, first-year enrollees in 2001 were all slightly higher than they were in 2000. Women were approximately 42 percent of the applicants and first-time, first-year enrollees in 2001, up slightly from 2000. Underrepresented minorities comprised over 12.6 percent of the applicants and 11.9 percent of the first-time, first-year enrollees, also up slightly from 2000.

Adult↗

PubMed1991

[Selective hematoporphyrin derivative (HMD) application in arterial vessels using a porous balloon catheter results in equivalent levels as compared to high-dose systemic administration].

The treatment of atherosclerotic vascular stenosis with percutaneous angioplasty is limited by a rate of restenosis of about 20-40%, in spite of new angioplasty devices. Histological and immune histological examinations of restenosed material obtained by coronary atherectomy indicate that cellular proliferation is an important determinant of restenosis. With the use of photodynamic therapy (PDT), it might be possible to selectively impair proliferating tissue by the application of the photosensitizer Photofrin II (a hematoporphyrin-derivative, HPD) followed by localized laser-light radiation. With the knowledge of the success of PDT in tumor therapy, the extension of the application of PDT in prophylaxis of restenosis should be examined. The technique used up to now works with the systemic application of the sensitizer. By applying HPD locally, however, one might be able to reduce the amount of the photosensitizer, but still achieve an equally cytotoxic effect. A recently developed catheter with a porous balloon enables local application of HPD. The following study describes the uptake and distribution of the hematoporphyrin-derivative Photofrin II within the walls of elastic and muscular type vessels after systemic and selective application. In 20 rabbits and seven pigs, Photofrin II was applied systemically (5 mg/kg i.v.) and locally (5 ml of 2.5 mg/ml). From each animal 12 vascular specimens (six arterial segments of either muscular and elastic type) were removed at a definite time within a defined period of 5 min to 24 h after application. To quantify the uptake of Photofrin II, we used fluorescence microscopy with digital image processing. After systemic application there was an increase of Photofrin II over a 4-h period. In contrast, a maximum concentration of Photofrin II was measured immediately after local application and found to be decreasing over a period of 4 h. The intima showed the highest uptake of HPD, both after local and systemic applications, as compared to uptake by the media and adventitia. The intimal uptake was significantly higher after local than after systemic application. Media and the adventitia showed, respectively, only one-half and one-fifth of the intima's intake. The rapid increase of the HPD concentration after local application would make PDT feasible in restenosis prophylaxis immediately after angioplasty without systemic side-effects of the photosensitizer.

Administration, Topical↗

PubMed2005

Cost considerations and applicant characteristics for the Pediatric Surgery Match.

BACKGROUND/PURPOSE: Formal training in pediatric surgery is highly competitive. The limited number of accredited positions has historically favored applicants with basic science experience, numerous publications, national presentations, and exposure to well-known pediatric surgeons. This review analyzes characteristics of successful applicants and cost associated with the Match. METHODS: A survey was e-mailed to 45 applicants after the 2003 Match. Geographic provenance, demographics, qualifications, costs, and valued program characteristics were assessed. Statistics were formulated by chi2 and Student's t test. RESULTS: Thirty-six applicants (80%) responded. Successful characteristics for matched vs unmatched included number of publications, 11.2 vs 5.7 (P < .01); first-author designation, 6.4 vs 3.1 (P = .02); basic science papers, 5.7 vs 1.7 (P < .01); national presentations, 5.8 vs 2.4 (P = .02); and presentations at pediatric surgical meetings, 2.0 vs 0.6 (P = .04). Ninety percent of matched applicants took time off to perform basic science research (P < .01). Average candidate expense was $6974, which represented 14% of pretax salary. Forty-one percent of applicants noted that cost limited the number of interviews taken. Fifty percent preferred a regional interview process to limit expense. Candidates ranked case diversity, volume, and mentor's advice as the most valued program characteristics. Successful applicants matched at their fifth rank on average. Eighty-six percent of unsuccessful applicants will reapply. CONCLUSIONS: Results of this study are important to those interested in the future of pediatric surgery. Successful applicants were shown to have several national presentations and multiple scientific publications, especially in basic sciences. Applicant costs are high, totaling more than $236,000 for survey respondents.

Adult↗

PubMed1996

Misrepresentation of research publications among emergency medicine residency applicants.

STUDY OBJECTIVE: To assess the prevalence of misrepresented citations among emergency medicine residency applicants and to determine whether misrepresentation increases as the number of citations increases. METHODS: We examined 350 consecutive emergency medicine residency applications and then reviewed all cited publications to determine whether they were genuine or misrepresented. Applicants with citations were divided into three groups: those who listed one citation, those with two to four citations, and those with five or more citations. The numbers of individuals and misrepresentations were then tabulated and compared among the groups. RESULTS: Publications were cited on 113 applications (32.3%). Twenty-three applicants (20.4% of those who cited publications and 6.6% of all applicants) misrepresented citations. Misrepresentations were found in 8 of 56 applications listing single citations (14.3%), 8 of 46 applications (17.4%) claiming two to four citations, and 7 of 11 (63.6%) applications claiming five or more citations (P=.00081, Pearson chi 2 test). CONCLUSION: Emergency medicine residency applications may contain misrepresented citations. The number of misrepresentations in this study increased as the number of citations increased.

Adult↗

PubMed2002

The review of drug applications submitted to the European Medicines Evaluation Agency: frequently raised objections, and outcome.

OBJECTIVE: To study the issues raised during the review of drug applications submitted to the European Medicines Evaluation Agency for approval in the European Union and to identify important predictors of outcome. METHODS: All consecutive applications submitted since September 1997 and which had reached an outcome by May 2001 were included. The factors considered in this exploratory analysis were: year of submission, anatomical therapeutic chemical classification (ATC code), type of medicinal product (biopharmaceuticals vs. new chemical entities), and common "major objections" raised during the review. Predictors were identified using multivariate logistic regression on outcome (positive opinion vs. negative opinion or withdrawal). Examples have been provided to illustrate some of the weaknesses of the applications received, the types of objections raised by the reviewers, and the strategies used to address them. RESULTS: This series consisted of 111 successive applications for which the review had started between September 1997 and April 2000. It included 73 (66%) new chemical entities and 38 (34%) biopharmaceuticals, the most represented agents being anti-neoplastic and immunomodulating agents, and anti-infectives for systemic use, with 25 (22%), and 19 (17%) applications, respectively. Overall the proportion of drug applications that failed to reach a positive outcome was 32/111 (29%). The most frequent major objections raised were those related to the safety database and to serious adverse events. These clinical safety objections were raised in 54 (48.6%) applications. Another frequent objection was the clinical efficacy objection on the lack of adequate randomised controlled trials, which was raised in 47 (42.3%) applications. This clinical efficacy objection was the only factor that was retained after multivariate selection (P<0.01). The odds of a positive outcome for an application lacking adequate randomised controlled trials were: 0.46 (95% confidence interval 0.29-0.71) times the odds of an application without this objection (P=0.0006). CONCLUSIONS: Despite the existence of various mechanisms that allow important deficiencies to be resolved, failure to establish clinical efficacy due to the lack of adequate randomised controlled trials remained problematic, leading to a high risk of rejection.

Clinical Trials as Topic↗

PubMed2006

Topical bioavailability of triamcinolone acetonide: effect of dose and application frequency.

The application frequency of topical corticosteroids is a recurrently debated topic. Multiple-daily applications are common, although a superior efficacy compared to once-daily application is not unequivocally proven. Only few pharmacokinetic studies investigating application frequency exist. The aim of the study was to investigate the effect of dose (Experiment 1) and application frequency (Experiment 2) on the penetration of triamcinolone acetonide (TACA) into human stratum corneum (SC) in vivo. The experiments were conducted on the forearms of 15 healthy volunteers. In Experiment 1, single TACA doses (300 microg/cm(2) and 100 microg/cm(2)) dissolved in acetone were applied on three sites per arm. In experiment 2, single (1 x 300 microg/cm(2)) and multiple (3 x 100 microg/cm(2)) TACA doses were similarly applied. SC samples were harvested by tape stripping after 0.5, 4 and 24 h (Experiment 1) and after 4, 8 and 24 h (Experiment 2). Corneocytes and TACA were quantified by UV/VIS spectroscopy and HPLC, respectively. TACA amounts penetrated into SC were statistically evaluated by a paired-sample t-test. In Experiment 1, TACA amounts within SC after application of 1 x 300 microg/cm(2) compared to 1 x 100 microg/cm(2) were only significantly different directly after application and similar at 4 and 24 h. In Experiment 2, multiple applications of 3 x 100 microg/cm(2) yielded higher TACA amounts compared to a single application of 1 x 300 microg/cm(2) at 4 and 8 h. At 24 h, no difference was observed. In conclusion, using this simple vehicle, considerable TACA amounts were retained within SC independently of dose and application frequency. A low TACA dose applied once should be preferred to a high dose, which may promote higher systemic exposure.

Adhesives↗

PubMed2005

Lateral thermal damage to rat abdominal wall after harmonic scalpel application.

BACKGROUND: Use of the Harmonic Scalpel transduces a lower amount of energy to tissues, thereby limiting the potential for lateral thermal damage and deep penetration because only low temperatures are reached. The working principle of the Harmonic Scalpel is the transformation of electric power into the longitudinal mechanical movement of the instrument tip. This study aimed to determine the effects from varying durations of Harmonic Scalpel application on the experimental model of rat abdominal wall without skin. METHODS: After the rats had been anesthetized, and a laparotomy was performed. The Harmonic Scalpel shears were used on the muscular part of the abdominal wall without skin. Different durations of output power 3 were applied: a single 5-s application, a single 10-s application, and a regimen of two sequential 5-s applications. Each animal in each group of 10 received five individual activations, after which the animals were killed. Tissue samples were fixed and embedded in paraffin before sections were taken and stained. Using light microscopy and morphometric imaging analysis, the width of tissue lateral thermal damage was measured from the point of Harmonic Scalpel incision. RESULTS: The rat abdominal wall showed lateral thermal damage over a mean width of 0.0522 +/- 0.0097 mm after a 5-s Harmonic Scalpel application, a damage width of 0.1544 +/- 0.0419 mm after a 10-s application, and a damage width of 0.1020 +/- 0.0430 mm after a 5-s application followed by 5 s of inactivity and another 5 s of activity. These differences in thermal damage width between all the groups are statistically significant. CONCLUSIONS: The findings lead to the conclusion that tissue lateral thermal damage after Harmonic Scalpel application at standard output power is greater when a longer sustained period of application is used. Lateral thermal damage also is greater if the Harmonic Scalpel application time is continuous rather than of the same total duration with a brief midpoint interruption.

Abdominal Injuries↗

PubMed1995

Nutrient run-off following application of livestock wastes to grassland.

Three types of farm waste (cattle slurry, dirty water and farm yard manure (FYM)) were applied to hydrologically isolated grassland plots on a sloping poorly draining soil. Two applications were made, the first in October and the second in February. Application rates were 50 m(3) ha(-1) of slurry and dirty water and 50 t ha(-1) of FYM. Volumes of run-off following rainfall events and concentrations of N, P and K in run-off were measured. Losses of nutrients were higher following applications made with the soil at field capacity and rainfall soon after application. In terms of percentage loss of applied nutrients, losses were generally low. Concentration of N in run-off from the dirty water and FYM treated plots following the first application and the slurry treated plots following the second application exceeded 11.3 mg dm(-3) (a recommended limit for drinking water) although the maximum concentration recorded was 15 mg dm(-3) following FYM application. Concentration of P in run-off only exceeded 1 mg dm(-3) following the second application of cattle slurry. Concentration of K exceeded 10 mg dm(-3) following the first application of FYM and the second application of cattle slurry.

Journal Article↗

PubMed1991

Design of a plastic minicolpostat applicator with shields.

A plastic intracavitary applicator system for the treatment of cancer of the uterine cervix is described. This applicator has a minicolpostat and a mechanism for affixing the tandem to the colpostats. Traditional afterloading refers only to the radioactive source. Both the source and the ovoid shield are afterloaded together in this applicator in contrast to traditional afterloading systems which afterload the source alone. A potential advantage of our applicator system is that it allows high quality CT localization because the sources and shields can be removed and the applicator is made of plastic. The advantages and disadvantages of this variation to the Fletcher system as well as other aspects of applicator design are discussed. An experimentally verified dose calculation method for shielded sources is applied to the design problems associated with this applicator. The dose distribution calculated for a source-shield configuration of the plastic applicator is compared to that obtained with a commercial Fletcher-Suit-Delclos (FSD) applicator. Significant shielding improvements can be achieved for the smallest diameter ovoid, that is, in the minicolpostat. The plastic minicolpostat dose distributions are similar to those produced by the conventional larger diameter colpostats. In particular, the colpostat shielding for rectum and bladder, which is reduced in the metal applicator's minicolpostat configuration, is maintained for the plastic minicolpostat. Further, it is shown that, if desired, relative to the FSD minicolpostat, the mucosa dose can be reduced by a suitable change of the minicolpostat source position.

Brachytherapy↗

PubMed2006

The optimization of dose delivery for intraoperative high-dose-rate radiation therapy using curved HAM applicators.

BACKGROUND AND PURPOSE: To determine the effect of the curvature of Harrison-Anderson-Mick applicators on the dose distribution in high-dose-rate intraoperative radiation therapy (HDR-IORT). MATERIAL AND METHODS: Treatment planning was performed with flat applicators using (192)Ir as the radioactive source, and dwell times were optimized using dose-point optimization techniques. These optimized dwell times were then used for the curved applicators, and the dose distributions that would actually be delivered to patients were determined. RESULTS: The dose directly below the central catheter was strongly dependent on the curvature of the applicator. Steep parabolic curves caused underdoses of as much as 19% at a point 1cm from the convex side of the applicator. The rate of dose reduction with increasing distance from the applicator surface was also a function of the curvature of the applicator. CONCLUSIONS: The curvature of the applicator profoundly affects dosimetry and can be exploited to optimize coverage of the target during HDR-IORT procedures. To ensure accurate dose delivery, these dose perturbations must be accounted for in the planning process. We recommend maintaining a dosimetry atlas of various applicator sizes and curvatures in addition to one for flat applicators.

Brachytherapy↗

PubMed1998

Monte Carlo calculation of the dose distributions of two 106Ru eye applicators.

BACKGROUND AND PURPOSE: Beta emitting 106Ru applicators are widely used to treat choroidal melanoma. In view of the importance of clinical applications of this radioisotope and the relative lack of knowledge of the dose distributions, three-dimensional dose maps of two concave applicators were calculated by means of Monte Carlo simulation. MATERIALS AND METHODS: Simulations of small CCA and CCB concave applicators manufactured by Bebig were performed using the Monte Carlo code PENELOPE, which allows the description of the structure (geometry and materials) of the applicator in detail. Electrons are emitted from the 106Ru nuclei isotropically, with initial energy randomly sampled from the corresponding Fermi spectra and with initial positions uniformly distributed on the radioactive layer. Primary electrons, as well as the produced delta-rays, are assumed to be absorbed in the medium when they slow down to an energy of 70 keV. Bremsstrahlung photons with energies larger than 7 keV are also simulated. The simulation code has been run on a 166 MHz PENTIUM PC. RESULTS: Three-dimensional dose distributions produced by the CCA and CCB applicators in a water sphere, concentric with the applicator, were evaluated. To minimize the magnitude of statistical uncertainties, advantage has been taken of the cylindrical symmetry of the problem. The relative depth-dose (along the symmetry axis of the applicator) was also evaluated from the applicator surface up to distances larger than I cm, with statistical uncertainties of a few percent. Results compare well with data supplied by the manufacturer. CONCLUSIONS: We have performed accurate Monte Carlo calculations of three-dimensional dose distributions from CCA and CCB 106Ru applicators. The results, presented in the form of two-dimensional maps, depth-dose distributions along the symmetry axis and lateral dose profiles, provide a detailed description of the dose delivered in treatments of choroidal melanoma.

Brachytherapy↗

PubMed1998

Spatial reproducibility of the ring and tandem high-dose rate cervix applicator.

PURPOSE: High-dose rate (HDR) applicators for uterine cervix brachytherapy are used with increasing frequency. Because multiple HDR fractions are required for treatment, the applicator position reproducibility is of most importance. To study this effect, the clinical data from patients with uterine cervix cancer were examined retrospectively to evaluate the interfraction geometric variation of the HDR applicator and its potential treatment impact. METHODS AND MATERIALS: Eighteen patients with invasive cervical cancer who were treated with definitive radiotherapy at William Beaumont Hospital were included in the study. Patients were treated with 45-50.4 Gy megavoltage external beam to the pelvis, and 35 Gy to the prescription point A from 7 fractions of HDR brachytherapy. The 3-dimensional (3D) interfraction geometrical variation of the ring and tandem (R & T) applicator was measured using predefined reference points in the 7 sets of orthogonal simulation films obtained prior to each HDR application. Spatial reproducibility of the R & T insertion and time-trend of the R & T position variation related to patient's anatomy during the treatment course were analyzed with respect to different groups of patients who had either early or advanced disease. RESULTS: The translational variation of the applicator position for all patients was 6.5, 5.9, and 7.7 mm (one standard deviation), respectively, in the patient's superior-to-inferior (SI), right-to-left lateral (RL), and anterior-to-posterior (AP) direction. The rotational variation was 3.4, 4.6, and 6.0 degrees (one standard deviation) in the patient's coronal, transverse, and sagittal planes. When the patients were grouped based on early disease or advanced disease, the latter demonstrated substantially larger variation (factor of 2) in the applicator position than the former. Furthermore, the time-trend of position variation was observable for both groups of patients. The variations occurred primarily during the first 3 fractions. CONCLUSIONS: Based on the good spatial reproducibility observed in our study, the current clinical procedure for the HDR R & T applicator placement is reliable. Positional reproducibility of the R & T applicator is highly dependent upon the size of tumor volume, which, in turn, deviates the applicator during the early course of HDR brachytherapy. Attention to the construction of the midline block is of paramount importance.

Brachytherapy↗

PubMed2006

Factors influencing applicant ranking of orthodontic programs.

Orthodontic programs spend considerable amounts of effort to attract, recruit, and interview the best and brightest applicants. Applicants and programs submit ranked preferences, and resident positions are filled by a computerized matching system (Match). The specific aims of this study were to determine the relative importance of certain factors in applicants' Match ranking of orthodontic programs and differences between orthodontic program directors' perceptions and actual factors cited by applicants influencing their ranking of orthodontic programs. Surveys were mailed to 55 orthodontic program directors and 478 applicants participating in the 2002 orthodontic Match. Forty-nine program director (89%) and 224 applicant (47%) surveys were returned. Rankings and importance of factors cited by applicants in their decision-making process and perceptions of those factors cited by program directors were compared. Applicants' top three factors were: "satisfied current residents," "multiple techniques taught," and "good quality of clinical facility." Program directors' perceived top three factors were: satisfied current residents, "good program reputation," and "good impression of current residents at interview." Comparing program directors' perceptions vs applicants' factors overall, the two groups were statistically different (P < .0001). Factors that stood out for their differences included: "GRE required or emphasized" (P < .0002), multiple techniques taught (P < .0007), and "good location" (P < .0008). Despite these differences, there was generally a high level of overall agreement between program directors' perceptions and factors actually influencing applicants' ranking of orthodontic programs.

Adult↗

PubMed1999

Photobiological aspects of sunscreen re-application.

A single application of a high sun protection factor (SPF) sunscreen has been shown to prevent sunburn, but the existence of a further protective effect following re-application of sunscreen has received little attention. The aim of this study was to quantify the ultraviolet radiation (UVR) protection against sunburn afforded by a re-application of sunscreen relative to a single application. The study methods were based on the Australian Standard SPF testing regimen, using human volunteers, standardized applications of sunscreen and an artificial solar simulating UVR source. Sunscreen was initially applied, followed by a suberythemal UVR dose; sunscreen was then re-applied, followed immediately by a second period of controlled UV exposure sufficient to induce mild erythema. Compared to the first application, the second sunscreen application afforded 3.1 times more protection against minimal UVR-induced erythema. The combined effect of two sunscreen applications gave on average 2.5 times better protection from UVR than a single sunscreen application. Health authorities worldwide have recommended sunscreen re-application for the prevention of sunburn for some time. This is the first quantitative study to substantiate such recommendations.

Administration, Topical↗

PubMed2006

Multilayer conformal applicator for microwave heating and brachytherapy treatment of superficial tissue disease.

PURPOSE: The purpose of this study was to construct and perform preliminary functionality evaluations of a multilayer conformal applicator with provisions for thermal monitoring, tight conformity and simultaneous microwave heating and brachytherapy treatment of large-area contoured surfaces. MATERIALS AND METHODS: The multilayer conformal applicator consists of thermal monitoring catheters for fibre-optic monitoring of skin temperatures, a waterbolus, a PCB microwave antenna array, a dielectric spacer for brachytherapy considerations, brachytherapy catheters for delivering HDR radiation and an inflatable air bladder for improving conformity to contoured surfaces. The applicator also includes an elastic attachment structure to hold the applicator securely in place on the patient. The conformity of the applicator to irregular surfaces was evaluated through CT imaging of the applicator fitted onto a life-sized human torso phantom. The fluid flow dynamics of the waterbolus, which impact the effectiveness of temperature control, were evaluated with thermometry during a 19 degrees C step change temperature of the circulating water. RESULTS: CT imaging showed improved conformity to the torso phantom surface following the application of gentle inward pressure from inflating the outer air bladder. Only a small number of 1-5 mm sized air gaps separated the conformal applicator and tissue surface. Thermometry testing of the bolus fluid flow dynamics demonstrated temperature uniformity within +/-0.82 degrees C across a 19 x 34 x 0.6 cm area bolus and +/-0.85 degrees C across a large 42 x 32 x 0.6 cm area bolus. CONCLUSION: CT scans of the applicator confirmed that the applicator conforms well to complex body contours and should maintain good conformity and positional stability even when worn on a mobile patient. Thermometry testing of two different waterbolus geometries demonstrated that uniform circulation and temperature control can be maintained throughout large, complex bolus shapes.

Brachytherapy↗

PubMed1990

Preclinical evaluation of submillimeter diameter microwave interstitial hyperthermia applicators.

Ultra miniature coaxial cable has been used, with microscopic techniques, to fabricate interstitial hyperthermia applicators having diameters of 0.20 mm, 0.33 mm, and 0.58 mm; commercial applicators have a diameter of 1.1 mm. Animal studies with the 0.33 mm diameter applicators have shown that they produce less local tissue trauma than the larger-diameter devices. All of these applicators operate at 915 MHz and have similar heating patterns because they use the conventional monopole design and the catheters have been approximately scaled to the dimensions of each size applicator. We have measured the heating (SAR) patterns of these applicators in tissue-simulating phantoms, both singly and in arrays, using a miniature electric field probe. As an intermediate step to patient trials, we have examined the ability of these applicators to provide effective heating of perfused tissue, using pig thigh and liver as models. Test results suggest that the durability and power handling capabilities of our submillimeter applicators are adequate for use in patients. These new applicators should be useful in the percutaneous treatment of deep-seated tumors and in intraoperative treatments. The applicators also permit intraluminal or intravascular access to tumors.

Animals↗

PubMed2001

Remobilization and uptake of N by newly planted apple (Malus domestica) trees in response to irrigation method and timing of N application.

Environmentally sound management of N in apple orchards requires that N supply meets demand. In 1997, newly planted apple trees (Malus domestica Borkh. var. Golden Delicious on M.9 rootstock) received daily applications of N for six weeks as Ca(15NO3)(2) through a drip irrigation system at a concentration of 112 mg l(-1) at 2-8, 5-11 or 8-14 weeks after planting. Irrigation water was applied either to meet estimated evaporative demand or at a fixed rate. In 1997, trees were harvested at 5, 8, 11 and 14 weeks after planting; and in 1998 at 3 weeks after full bloom. The amount of fertilizer N recovered was similar in trees in both irrigation treatments, but efficiency of fertilizer use was greater for trees receiving demand-controlled irrigation than fixed-rate irrigation. This was attributed to lower N inputs, greater retention time in the root zone and less N leaching in the demand-controlled irrigation treatments compared with fixed-rate irrigation treatments. Less fertilizer N was recovered by trees receiving an early application of N than a later application of N and this was related to the timing of N supply with respect to tree demand. Demand for root-supplied N was low until 11 weeks after planting, because early shoot and root growth was supported by N remobilized from woody tissue, which involved 55% of the total tree N content at planting. Rapid development of roots > 1 mm in diameter occurred between 11 and 14 weeks after planting, after remobilization ended, and was greater for trees receiving an early application of N than for trees receiving a later application of N. Late-season tree N demand was supplied by native soil N, and uptake and background soil solution N concentrations were higher for trees receiving demand-supplied irrigation compared with fixed-rate irrigation. Total annual N uptake by roots was unaffected by treatments and averaged 6-8 g tree(-1). Nitrogen applications in 1997 affected growth and N partitioning in 1998. Trees receiving early applications of N had more flowers, spur leaves and bourse shoots than trees receiving later applications of N. Consequently, more N was remobilized into fruits in trees receiving early applications of N compared with fruits in trees receiving later applications of N. Demand for N in the young apple trees was low. Early season demand was met by remobilization from woody tissues and the timing of demand for root-supplied N probably depends on whether flowering occurs. Method of N delivery affected the efficiency of N use. We conclude that N demand can be met at soil solution N concentrations of around 20 mg l(-1).

Agriculture↗

PubMed2001

Ex vivo evaluation of novel miniaturized laser-induced interstitial thermotherapy applicators for effective small-volume tissue ablation.

RATIONALE AND OBJECTIVES: For effective small-volume tissue ablation in clinical and experimental settings, smaller laser-induced interstitial thermotherapy (LITT) applicator designs are required. The aim of this study was to compare the ablation properties of recently developed ultrasmall and small to standard LITT applicators. METHODS: Laser-induced interstitial thermotherapy was performed on liver samples using ultrasmall, small, and standard LITT applicators. Thermotherapy was monitored by magnetic resonance imaging, and lesion sizes were measured for each image. True lesion sizes were then determined macroscopically and by histology. RESULTS: For continuous laser application over 5 minutes, maximum power settings were 5 W for the ultrasmall and small applicators and 10 W for the standard applicator. Given identical LITT settings, lesion volume measured by magnetic resonance imaging was significantly larger and histological tissue damage was more severe with the ultrasmall and small applicators than with the standard applicator. CONCLUSIONS: Small and ultrasmall LITT applicators can be used for effective tissue ablation of small target volumes in experimental and clinical applications.

Animals↗