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Lee J, Van Loozen A, Sweeney D, Schneck F, Ching CB. The projected impact of COVID-19 on global surgical care: A case study of International Volunteers in Urology (IVUmed). J Glob Health 2022; 12:03086. [PMID: 36527280 PMCID: PMC9758536 DOI: 10.7189/jogh.12.03086] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Affiliation(s)
- John Lee
- Joe R. & Teresa Lozano Long School of Medicine, University of Texas Health Science Center at San Antonio, San Antonio, Texas, USA
| | | | | | - Francis Schneck
- Division of Pediatric Urology, University of Pittsburgh, Pittsburgh, Pennsylvania USA
| | - Christina B Ching
- Department of Pediatric Urology, Nationwide Children’s Hospital, Columbus, Ohio USA
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Villanueva J, Pifer B, Colaco M, Grajales V, Ayyash O, Chaudhry R, Schneck F, Cannon G, Fox J. A government mandated consent safely reduces opioid utilization for major pediatric genitourinary surgeries. J Pediatr Surg 2021; 56:2086-2093. [PMID: 33454082 DOI: 10.1016/j.jpedsurg.2021.01.004] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/05/2020] [Revised: 12/25/2020] [Accepted: 01/01/2021] [Indexed: 01/14/2023]
Abstract
INTRODUCTION We describe the effect of a state mandated opioid consent on opioid utilization and multimodal pain use for major pediatric genitourinary surgeries. METHODS All patients who underwent an inpatient pediatric genitourinary surgery at the Children's Hospital of Pittsburgh between August 2015 and February 2020 were identified. Inpatient and outpatient multimodal pain control utilization were assessed. Delayed prescriptions or emergency department visits within 30 days were identified and when applicable referenced against National Surgical Quality Improvement Program data. RESULTS After accounting for a 6-month transition period following policy implementation, 462 major pediatric genitourinary procedures were identified. The frequency of discharge opiate prescriptions decreased from 68.4% prior to the transition period to 10.7% afterward(p<0.001). Morphine milligram equivalents per prescription decreased from 75(IQR 45-150) to 45(IQR 22.5-75)(p<0.001). The rate of delayed non-opioid analgesic prescriptions (6.6% vs 7.4%), delayed opioid prescriptions (1.5% vs 0.3%), or emergency department visits (11.8% vs 12.6%)(p = 0.809) remained unchanged. Data agreed with National Surgical Quality Improvement Program data in 98.5% of cases. After excluding one surgeon who departed after the transition period, regional block utilization did not change from 61/115(53%) to 147/320(45.9%)(p = 0.425). CONCLUSIONS A state mandated opioid consent safely reduced opioid utilization for most major pediatric genitourinary surgeries. LEVEL OF EVIDENCE Level III.
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Affiliation(s)
- Jeffrey Villanueva
- Division of Urology, Children's Hospital of Pittsburgh of the University of Pittsburgh Medical Center, 4401 Penn Ave, Pittsburgh, PA, USA.
| | - Benjamin Pifer
- University of Pittsburgh School of Medicine, 3550 Terrace St, Pittsburgh, PA, USA
| | - Marc Colaco
- Division of Urology, Children's Hospital of Pittsburgh of the University of Pittsburgh Medical Center, 4401 Penn Ave, Pittsburgh, PA, USA
| | - Valentina Grajales
- Department of Urology, University of Pittsburgh Medical Center, 3471 Fifth Avenue, Pittsburgh, PA, USA
| | - Omar Ayyash
- Department of Urology, University of Pittsburgh Medical Center, 3471 Fifth Avenue, Pittsburgh, PA, USA
| | - Rajeev Chaudhry
- Division of Urology, Children's Hospital of Pittsburgh of the University of Pittsburgh Medical Center, 4401 Penn Ave, Pittsburgh, PA, USA
| | - Francis Schneck
- Division of Urology, Children's Hospital of Pittsburgh of the University of Pittsburgh Medical Center, 4401 Penn Ave, Pittsburgh, PA, USA
| | - Glenn Cannon
- Division of Urology, Children's Hospital of Pittsburgh of the University of Pittsburgh Medical Center, 4401 Penn Ave, Pittsburgh, PA, USA
| | - Janelle Fox
- Division of Urology, Children's Hospital of Pittsburgh of the University of Pittsburgh Medical Center, 4401 Penn Ave, Pittsburgh, PA, USA
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Villanueva J, Pifer B, Colaco M, Fox J, Chaudhry R, Schneck F, Cannon G. Point-of-care ultrasound is an accurate, time-saving, and cost-effective modality for post-operative imaging after pyeloplasty. J Pediatr Urol 2020; 16:472.e1-472.e6. [PMID: 32586774 DOI: 10.1016/j.jpurol.2020.05.156] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/24/2020] [Revised: 05/10/2020] [Accepted: 05/17/2020] [Indexed: 12/26/2022]
Abstract
BACKGROUND Dismembered pyeloplasty is considered the gold standard treatment for ureteropelvic junction obstruction (UPJO). Although the frequency and timing of follow up imaging after pyeloplasty is variable, renal ultrasound (RUS) is commonly utilized. With minimal training, point-of-care ultrasound (POCUS) can be easily performed by a urologist during a post-operative visit. OBJECTIVE Our hypothesis is that POCUS is an accurate, time-saving, and cost-effective alternative to a complete retroperitoneal ultrasound (CRUS) performed by the Radiology Department after pyeloplasty. STUDY DESIGN The clinical records of all children who underwent pyeloplasty (by any method) over a 12 month period at our institution were retrospectively reviewed. The exact timing and method (POCUS vs. CRUS) of follow up imaging was surgeon-dependent. Statistical analysis was performed to compare the time and cost of POCUS vs. CRUS. The clinical course of each patient who had each type of imaging was assessed. RESULTS A total 45 patients were included in this analysis. Over a mean follow up period of 29 months, a total of 73 CRUS and 67 POCUS were performed. Each CRUS on average added 2 h to each patient's healthcare encounter. Had the 73 CRUS been performed as POCUS instead, this would have corresponded to $83,751 less charges to payers. There was no difference in the rate of the detection of worsening, stable, or improved hydronephrosis (HN) between either modality (p > 0.05). The recommended follow up time for observed HN was no different between CRUS and POCUS (p > 0.05). Children with worsening HN on POCUS underwent functional studies without confirmatory CRUS. Interestingly, two patients had metachronous, contralateral UPJO discovered during post-operative imaging. These were both discovered by POCUS. Nineteen (42%) patients who had attended at least one post-operative visit were eventually loss to follow-up. This occurred exclusively in those who did not have worsening ultrasound (p < 0.01). There was no difference in the loss to follow-up after POCUS (8) or CRUS (12) (p > 0.05). CONCLUSIONS POCUS performed by a urologist is an accurate assessment of HN after pyeloplasty with time and cost savings to compared to a CRUS performed by a radiologist. POCUS is not associated with any difference in rate of detection of worsening HN or rate of loss to follow up.
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Affiliation(s)
- Jeffrey Villanueva
- Division of Pediatric Urology, UPMC Children's Hospital of Pittsburgh, 4401 Penn Avenue, Pittsburgh, PA, USA 15224.
| | - Benjamin Pifer
- University of Pittsburgh School of Medicine, Pittsburgh, PA, USA 15213
| | - Marc Colaco
- Division of Pediatric Urology, UPMC Children's Hospital of Pittsburgh, 4401 Penn Avenue, Pittsburgh, PA, USA 15224
| | - Janelle Fox
- Division of Pediatric Urology, UPMC Children's Hospital of Pittsburgh, 4401 Penn Avenue, Pittsburgh, PA, USA 15224
| | - Rajeev Chaudhry
- Division of Pediatric Urology, UPMC Children's Hospital of Pittsburgh, 4401 Penn Avenue, Pittsburgh, PA, USA 15224
| | - Francis Schneck
- Division of Pediatric Urology, UPMC Children's Hospital of Pittsburgh, 4401 Penn Avenue, Pittsburgh, PA, USA 15224
| | - Glenn Cannon
- Division of Pediatric Urology, UPMC Children's Hospital of Pittsburgh, 4401 Penn Avenue, Pittsburgh, PA, USA 15224
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Villanueva J, Pifer* B, Colaco M, Fox J, Schneck F, Chaudhry R, Cannon G. MP71-17 POINT OF CARE ULTRASOUND IS AN ACCURATE, TIME-SAVING, AND COST-EFFECTIVE MODALITY FOR POSTOPERATIVE IMAGING AFTER PYELOPLASTY. J Urol 2020. [DOI: 10.1097/ju.0000000000000951.017] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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Garcia A, Garcia A, Vollrath S, Schneck F, Silva C, Marchetti Í, Vieira J. Spatial diet overlap and food resource in two congeneric mullet species revealed by stable isotopes and stomach content analyses. COMMUNITY ECOL 2018. [DOI: 10.1556/168.2018.19.2.3] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Affiliation(s)
- A.F.S. Garcia
- Programa de Pós-Graduação em Biologia de Ambientes Aquáticos Continentais. Universidade Federal do Rio Grande, Rio Grande, Brazil
| | - A.M. Garcia
- Instituto de Oceanografia, Universidade Federal do Rio Grande, Rio Grande, Brazil
| | - S.R. Vollrath
- Programa de Pós-Graduação em Biologia de Ambientes Aquáticos Continentais. Universidade Federal do Rio Grande, Rio Grande, Brazil
| | - F. Schneck
- Instituto de Ciências Biológicas, Universidade Federal do Rio Grande, Rio Grande, Brazil
| | - C.F.M. Silva
- Programa de Pós-Graduação em Biologia de Ambientes Aquáticos Continentais. Universidade Federal do Rio Grande, Rio Grande, Brazil
| | - Í.J. Marchetti
- Instituto de Oceanografia, Universidade Federal do Rio Grande, Rio Grande, Brazil
| | - J.P. Vieira
- Instituto de Oceanografia, Universidade Federal do Rio Grande, Rio Grande, Brazil
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Benz K, Maruf M, Hatheway C, Kasprenski M, Jayman J, Docimo S, Schneck F, Gearhart J. The intravesical phallus in patients with cloacal exstrophy: An embryologic conundrum. J Pediatr Urol 2018; 14:428.e1-428.e5. [PMID: 29941348 DOI: 10.1016/j.jpurol.2018.05.001] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/27/2017] [Accepted: 05/17/2018] [Indexed: 11/16/2022]
Abstract
BACKGROUND Phalluses present inside the extrophied bladder of cloacal exstrophy (CE) newborns have been sporadically reported in the literature; this clinical entity has largely unknown origins and may represent an extremely rare anomaly of CE. OBJECTIVE Along with nearly doubling the number of reported intravesical phalluses in the literature, this study aims to outline the common anatomic features and discuss the implications for theories of CE embryogenesis. STUDY DESIGN The authors retrospectively identified patients with CE and a potential intravesical phallus between 1997 and 2017 at two high-volume centers. Information was obtained about karyotype, age at closure, neurologic and renal anomalies, diastasis, phallus anatomy, and phallus biopsy pathology. RESULTS Six genotypic males met the inclusion criteria. Five of six had a diastasis greater than 6 cm. Four of six had paired corporal bodies in the intravesical phallus, one had a single corporal body, and one had a corporal-like structure. Five of six patients had a phallus located midline in the caudal aspect of the bladder; one was located midline in the bladder dome. Phallic biopsies were obtained in three of six patients. Two showed glanular and corporal tissue while the other showed vascular proliferation morphologically similar to that of erectile tissue. DISCUSSION Previous reports suggested that a superior vesicle fissure configuration, fusion of the corporal bodies, and fused bladder plates were common findings with an intravesical phallus. With the addition of new cases, the only consistent variable between patients is a phallus located anywhere along the bladder plate that can comprise a corporal-like structure, a single corporal body, or fused corporal bodies. These findings have implications for several embryologic theories. Although this is a retrospective review with a limited number of patients, the condition is exceedingly infrequent making it only observable retrospectively over decades at high volume centers. CONCLUSIONS The study outlined common anatomic features of the intravesical phallus in cloacal exstrophy and discussed the subsequent embryologic implications. In cloacal exstrophy newborns with presumed aphallia, meticulous inspection of the bladder plate and biopsy of any potential phallic structures can prevent resection of phallic tissue.
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Affiliation(s)
- Karl Benz
- James Buchanan Brady Urological Institute, Division of Pediatric Urology, The Johns Hopkins School of Medicine, Baltimore, MD, USA
| | - Mahir Maruf
- James Buchanan Brady Urological Institute, Division of Pediatric Urology, The Johns Hopkins School of Medicine, Baltimore, MD, USA
| | - Clark Hatheway
- University of Pittsburgh School of Medicine, Pittsburgh, PA, USA
| | - Matthew Kasprenski
- James Buchanan Brady Urological Institute, Division of Pediatric Urology, The Johns Hopkins School of Medicine, Baltimore, MD, USA
| | - John Jayman
- James Buchanan Brady Urological Institute, Division of Pediatric Urology, The Johns Hopkins School of Medicine, Baltimore, MD, USA
| | - Steven Docimo
- Department of Pediatric Urology, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA
| | - Francis Schneck
- Department of Pediatric Urology, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA
| | - John Gearhart
- University of Pittsburgh School of Medicine, Pittsburgh, PA, USA.
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Dangle P, Salgado C, Reyes-Mugica M, Schneck F, Ost M, Sims-Lucas S. Testicular Hypoplasia Is Driven by Defective Vascular Formation. Urology 2016; 101:94-98. [PMID: 27765594 DOI: 10.1016/j.urology.2016.10.010] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2016] [Revised: 09/28/2016] [Accepted: 10/03/2016] [Indexed: 11/25/2022]
Abstract
OBJECTIVE To determine if vanishing testis could result from a fault in embryological development as a result of an arrest in endothelial cell migration rather than secondary to just a random physical torsion/twist. A testicular nubbin or vanishing testis is considered to be secondary to a neonatal torsion and is usually associated with a hemosiderin deposit. MATERIALS AND METHODS Cases of vanishing testis excision were compared with age-matched controls from cadaveric testes without known genitourinary pathology. To assess the testis microvasculature, we performed immunohistochemistry using an automated staining platform with controlled and standardized conditions and positive and negative controls. We used cluster of differentiation (CD) 34 to stain blood vessel endothelium, stem cells, and interstitium; CD31 (all endothelium); and D2-40 for lymphatic endothelium. Morphometric analysis was carried out, % of the total tissue with CD31 and CD34 positive stain was assessed, and the number of the lymphatic vessels (D2-40) per mm2 was counted. RESULTS Of the 10 cases, 7 had evidence of hemosiderin deposit and calcification. The % distribution of CD34 in controls was higher, 13.4 ± 3.1 (mean ± standard deviation), compared to nubbin cases, 4.5 ± 2.9 (P ≤ .001). The % distribution of CD31 was 2.8 ± 0.83 in controls compared to 1.31 ± 0.60 in cases (P ≤ .001). The lymphatic distribution was similar in both groups, cases (6.4 ± 4.3 n/mm2) and controls (6.4 ± 1.7 n/mm2) (P = .99) CONCLUSION: This histopathological study suggests that disturbances in endothelial development may be a contributing factor leading to testicular hypoplasia and a resultant nubbin testis, independent of a physical torsion event.
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Affiliation(s)
- Pankaj Dangle
- Division of Pediatric Urology, Children's Hospital of Pittsburgh, University of Pittsburgh Medical Center, Pittsburgh, PA.
| | - Cláudia Salgado
- Department of Pathology, Children's Hospital of Pittsburgh, University of Pittsburgh Medical Center, Pittsburgh, PA
| | - Miguel Reyes-Mugica
- Department of Pathology, Children's Hospital of Pittsburgh, University of Pittsburgh Medical Center, Pittsburgh, PA
| | - Francis Schneck
- Division of Pediatric Urology, Children's Hospital of Pittsburgh, University of Pittsburgh Medical Center, Pittsburgh, PA
| | - Michael Ost
- Division of Pediatric Urology, Children's Hospital of Pittsburgh, University of Pittsburgh Medical Center, Pittsburgh, PA
| | - Sunder Sims-Lucas
- Department of Pediatrics, Children's Hospital of Pittsburgh, University of Pittsburgh Medical Center, Pittsburgh, PA
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Dangle P, Salgado DC, Reyes-Mugica M, Chaudhry R, Schneck F, Ost M, Sims-lucas S. MP43-20 TESTICULAR HYPOPLASIA IS DRIVEN BY DEFECTIVE VASCULAR FORMATION. J Urol 2016. [DOI: 10.1016/j.juro.2016.02.229] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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Correa A, Kang A, Dangle P, Stephany H, Cannon G, Schneck F, Ost M. MP55-20 IS THE USE OF SMALL STENTS SAFE IN FOLLOWING PYELOPLASTY? OUR EXPERIENCE WITH 3 FRENCH STENTS. J Urol 2016. [DOI: 10.1016/j.juro.2016.02.611] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Chaudhry R, Dangle P, Cannon G, Ost M, Schneck F, Stephany H. FRII-10 HISTORICAL PERSPECTIVES ON THE UROLOGIC MANAGEMENT OF SPINA BIFIDA PRE AND POST THE ADVENT OF CLEAN INTERMITTENT CATHETERIZATION. J Urol 2016. [DOI: 10.1016/j.juro.2016.02.2931] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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Roller F, Harth S, Schneck F, Rixe J, Krombach G, Schneider C. CTA der Koronararterien: Prävalenz des persistierenden foramen ovale (PFO) und anderer Formen von atrialen Septumdefekten (ASD). ROFO-FORTSCHR RONTG 2015. [DOI: 10.1055/s-0035-1550962] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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Dudley A, Dwyer M, Dangle P, Banihani O, Stephany H, Cannon G, Schneck F, Ost M. MP40-11 PROSPECTIVE ASSESSMENT OF PEDIATRIC RADIATION EXPOSURE: THE PEDIATRIC UROLOGY RADIATION SAFETY EVALUATION (PURSE) STUDY. J Urol 2015. [DOI: 10.1016/j.juro.2015.02.1193] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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Roller F, Harth S, Schneck F, Rixe J, Krombach G, Schneider C. Vorhersage des Revaskularisationserfolges bei CTO der Koronararterien mittels CTA: Entwicklung und initiale Evaluation eines Scoringsystems. ROFO-FORTSCHR RONTG 2014. [DOI: 10.1055/s-0034-1373578] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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Ristau B, Casella D, Banihani O, Fox J, Cannon G, Schneck F, Docimo S, Ost M. MP26-12 RADIATION EXPOSURE IN PEDIATRIC PATIENTS UNDERGOING EVALUATION AND MANAGEMENT OF NEPHROLITHIASIS. J Urol 2014. [DOI: 10.1016/j.juro.2014.02.900] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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Barbosa FG, Schneck F, Melo AS. Use of ecological niche models to predict the distribution of invasive species: a scientometric analysis. BRAZ J BIOL 2013; 72:821-9. [PMID: 23295510 DOI: 10.1590/s1519-69842012000500007] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2011] [Accepted: 01/25/2012] [Indexed: 03/28/2023] Open
Abstract
We conducted a scientometric analysis to determine the main trends and gaps of studies on the use of ecological niche models (ENMs) to predict the distribution of invasive species. We used the database of the Thomson Institute for Scientific Information (ISI). We found 190 papers published between 1991 and 2010 in 82 journals. The number of papers was low in the 1990s, but began to increase after 2003. One-third of the papers were published by researchers from the United States of America, and consequently, the USA was also the most studied region. The majority of studies were carried out in terrestrial environments, while only a few investigated aquatic systems, probably because important aquatic predictor variables are scarce or unavailable for most regions in the world. Species-occurrence records were mainly composed of presence-only records, and almost 70% of the studies were carried out with plants and insects. Twenty-three different distribution modelling methods were used. The Genetic Algorithm for Rule-set Production (GARP) was used most often. Our scientometric analysis showed a growing interest in the use of ENMs to predict the distribution of invasive species, especially in the last decade, which is probably related to the increase in species introductions worldwide. Among some important gaps that need to be filled, the relatively small number of studies conducted in developing countries and in aquatic environments deserves careful attention.
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Affiliation(s)
- F G Barbosa
- Programa de Pós-graduação em Ecologia, Instituto de Biociências, Universidade Federal do Rio Grande do Sul - UFRGS, CP 15007, CEP 91501-970, Porto Alegre, RS, Brazil.
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López M, Hofer H, Stock KD, Bermúdez JC, Schirmacher A, Schneck F, Kück S. Spectral reflectance and responsivity of Ge- and InGaAs-photodiodes in the near-infrared: measurement and model. Appl Opt 2007; 46:7337-7344. [PMID: 17932548 DOI: 10.1364/ao.46.007337] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
The spectral reflectance and responsivity of Ge- and InGaAs-photodiodes at (nearly) normal and oblique incidence (45 degrees) were investigated. The derived data allow a calculation of the photodiodes responsivities for any incident angle. The measurements were carried out with s- and p-polarized radiation in the wavelength range from 1260 to 1640 nm. The spectral reflectance of the photodiodes was modeled by using the matrix approach developed for thin-film optical assemblies. The comparison between the calculated and measured reflectance shows a difference of less than 2% for the Ge-photodiode. For the InGaAs-photodiode, the differences between measured and calculated reflectance are larger, i.e., up to 6% for wavelengths between 1380 and 1580 nm. Despite the larger differences between calculated and measured spectral reflectances for the InGaAs-photodiode, the difference between calculated and measured spectral responsivity is even smaller for the InGaAs-photodiode than for the Ge-photodiode, i.e., < or =1.2% for the InGaAs-photodiode compared to < or =2.2% for the Ge-photodiode. This is because the difference in responsivity is strongly correlated to the absolute spectral reflectance level, which is much lower for the InGaAs-photodiode. This observation also shows the importance of having small reflectances, i.e., appropriate antireflection coatings for the photodiodes. The relative standard uncertainty associated with the modeled spectral responsivity is about 2.2% for the Ge-photodiode and about 1.2% for the InGaAs-photodiode for any incident angle over the whole spectral range measured. The data obtained for the photodiodes allow the calculation of the spectral responsivity of Ge- and InGaAs-trap detectors and the comparison with experimental results.
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Affiliation(s)
- M López
- Optics Division, Physikalisch-Technische Bundesanstalt, 38116 Braunschweig, Germany.
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Abstract
Unilamellar vesicles are observed to form spontaneously at planar lipid bilayers agitated by exothermic chemical reactions. The membrane-binding reaction between biotin and streptavidin, two strong transmembrane neutralization reactions, and a weak neutralization reaction involving an "antacid" buffer, all lead to spontaneous vesicle formation. This formation is most dramatic when a viscosity differential exists between the two phases bounding the membrane, in which case vesicles appear exclusively in the more viscous phase. A hydrodynamic analysis explains the phenomenon in terms of a membrane flow driven by liberated reaction energy, leading to vesicle formation. These results suggest that energy liberated by intra- and extracellular chemical reactions near or at cell and internal organelle membranes can play an important role in vesicle formation, membrane agitation, or enhanced transmembrane mass transfer.
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Affiliation(s)
- D A Edwards
- Department of Chemical Engineering, Pennsylvania State University, University Park 16802, USA
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