Mapping tree distribution and LAI in peatlands using field methods and imaging spectroscopy: a case study for the Haaksbergerveen,the Netherlands

Leaf area index (LAI) is among the vegetation parameters that play an important role in climate, hydrological and ecological studies, and is used for assessing growth and expansion of vegetation. The main objective of this study was to develop a methodology to map the LAI distribution of birch trees (Betula pendula) in peatland ecosystems using field-based instruments and airborne-based remote-sensing techniques. The developed mapping method was validated using field-based LAI measurements using the LAI-2000 instrument. First vegetation indices, including simple ratio (SR), normalized difference vegetation index (NDVI), and reduced simple ratio (RSR), were derived from HyMap data and related to ground-based measurements of LAI. LAI related better with RSR (R² = 0.68), followed by NDVI (R² = 0.63) and SR (R² = 0.58), respectively. Areas with birch were identified using Spectral Angle Mapper (SAM) to classify the image into 11 end members of dominant species including bare soil and open water. Next, the relationship between LAI and RSR was applied to areas with birch, yielding a birch LAI map. Comparison of the map of the birch trees and field-based LAI data was done using linear regression, yielding an R² = 0.38 and an RMSE = 0.25, which is fairly accurate for a structurally highly diverse field situation. The method may prove an invaluable tool to monitor tree encroachment and assess tree LAI in these remote and poorly accessible areas.     

High-resolution crystal structures of delta5-3-ketosteroid isomerase with and without a reaction intermediate analogue

Bacterial Delta5-3-ketosteroid isomerase (KSI) catalyzes a stereospecific isomerization of steroid substrates at an extremely fast rate, overcoming a large disparity of pKa values between a catalytic residue and its target. The crystal structures of KSI from Pseudomonas putida and of the enzyme in complex with equilenin, an analogue of the reaction intermediate, have been determined at 1.9 and 2.5 A resolution, respectively. The structures reveal that the side chains of Tyr14 and Asp99 (a newly identified catalytic residue) form hydrogen bonds directly with the oxyanion of the bound inhibitor in a completely apolar milieu of the active site. No water molecule is found at the active site, and the access of bulk solvent is blocked by a layer of apolar residues. Asp99 is surrounded by six apolar residues, and consequently, its pKa appears to be elevated as high as 9.5 to be consistent with early studies. No interaction was found between the bound inhibitor and the residue 101 (phenylalanine in Pseudomonas testosteroni and methionine in P. putida KSI) which was suggested to contribute significantly to the rate enhancement based on mutational analysis. This observation excludes the residue 101 as a potential catalytic residue and requires that the rate enhancement should be explained solely by Tyr14 and Asp99. Kinetic analyses of Y14F and D99L mutant enzymes demonstrate that Tyr14 contributes much more significantly to the rate enhancement than Asp99. Previous studies and the structural analysis strongly suggest that the low-barrier hydrogen bond of Tyr14 (>7.1 kcal/mol), along with a moderate strength hydrogen bond of Asp99 ( approximately 4 kcal/mol), accounts for the required energy of 11 kcal/mol for the transition-state stabilization.     

Information from time-varying vibrotactile stimuli

Experiments have been carried out to investigate the information transfer available via a single vibrator on the fingertip. In a first experiment, for stimuli with durations 80 to 320 ms, discrimination of a one-octave step change in frequency at the halfway point was investigated. Results were similar for three stimulus types--sinewave, monophasic pulse and tetraphasic pulse--suggesting temporal cues are more important than spectral cues in this task. In a second experiment, subjects were required to perceive changes in a sequence of stimulus elements. A presentation rate of 6.25 elements s-1 was found to give better results than a rate of 12.5 elements s-1. In the former case, the potential information transfer per element was estimated to be approximately 1.0 bits, corresponding to an information transfer rate of around 6 bits s-1. Implications for the design of a tactile aid to lipreading are discussed.     

Complementary circuits based on solution processed low-voltage organic field-effect transistors

The field of organic electronics is advancing quickly towards ultra low-cost, low-end applications and is expected to provide the necessary technology required for flexible/printed electronics. Here we address the need for solution processed low-voltage complementary logic in order to reduce power consumption of organic circuits and hence enable their use in portable, i.e. battery-powered applications. We demonstrate both p- and n-channel solution processed high performance organic field-effect transistors that operate at voltages below |1.5| V. The reduction in operating voltage is achieved by implementing ultra-thin gate dielectrics based on solution processed self-assembled monolayers. This work demonstrates the feasibility of fabricating low-voltage complementary organic circuits by means of solution processing.     

Should laparoscopic appendectomy be avoided for complicated appendicitis in children?

BACKGROUND/PURPOSE: Laparoscopic appendectomy is becoming the preferred technique for treating acute appendicitis. However, recent literature on adults suggests that laparoscopic appendectomy may increase the risk for postoperative infectious complications in complicated (gangrenous or perforated) cases. This study was undertaken to compare the results of open versus laparoscopic appendectomy for complicated appendicitis in children. METHODS: A retrospective review from two institutions was performed for all children treated operatively for complicated appendicitis from January 1994 through November 1996. RESULTS: Fifty-six cases were identified. Twenty-seven children underwent laparoscopic appendectomy, whereas 22 underwent open appendectomy. Seven children underwent conversion from laparoscopic to open surgery. Operating times and length of hospital stay did not differ significantly between the laparoscopic and open groups. Postoperative complications developed in 24 children (42.8%). Complications were more frequent after laparoscopic appendectomy compared with open appendectomy (56% v 18%, P = .002). A postoperative intraabdominal abscess (IAA) developed in 14 children (25%). An IAA occurred in two children after open appendectomy compared with 11 children after laparoscopic appendectomy (9% v 41%, P = .01). CONCLUSION: The findings suggest that laparoscopic appendectomy should be avoided in children who have complicated appendicitis because of the increased risk for postoperative intraabdominal abscesses. The authors propose a prospective, randomized trial to verify this finding.     

Nonimmune hydrops fetalis: fetal and neonatal outcome during 1983-1992

Prognostic factors for survival of 62 fetuses and neonates with nonimmune hydrops fetalis (NIHF) were studied retrospectively. Twenty-eight infants survived >/=28 days which is 45% for all fetuses and newborns diagnosed with NIHF and 61% for liveborns with unresolved NIHF. Univariate analysis identified that mortality was associated with the presence of >/=2 serous cavity effusions and a need for chest compressions at birth. Multivariate logistic regression analysis confirmed that the presence of >/=2 serous cavity effusions was significantly associated with mortality from NIHF <28 days after birth [OR = 48.2 (CI 3.6, 662.9) (p < 0.004)]. We conclude that, compared to published cases from the 1970s and early 1980s, survival of liveborns with NIHF seems improved. The decrease in stillbirths is more notable. The severity of hydrops at birth is the key determinant for survival.     

Hypersensitivity reactions to use of mebeverine]

Twenty-one cases of adverse reactions to mebeverine use were reported to the Inspectorate for Health Care in the Netherlands since 1978. In 12 patients (five men and seven women) this was an immunological hypersensitivity reaction. All patients recovered after drug withdrawal. The time between start and onset of symptoms varied from several minutes to 14 days. Most reactions consisted of urticaria or maculopapular rash, sometimes accompanied by fever, polyarthritis, thrombopenia or angioedema. In contradiction to the manufacturer's claims adverse reactions to the use of mebeverine do occur.     

Provision of taxoids in 1996: inequality of care

OBJECTIVE: To inventory the utilization of taxoids in 1996. METHODS: A survey was conducted in february 1997 among the medical heads of 130 Dutch hospitals. The questions about the use of taxoids (paclitaxel and docetaxel) in 1996 concerned indications, numbers of patients treated, the funding and possible financial restrictions on the treatment. Three weeks after the mailing of the questionnaire, a reminder was sent to hospitals that had not responded. The data from 120 hospitals where oncological care was administered were analysed. RESULTS: Of the 120 hospitals, 111 (92.5%) returned the questionnaire, from 114 locations. Twelve locations reported not having used taxoids, four of them partly for financial reasons. Taxoids had been used at 102 locations: at the expense of the hospital budget at 101 locations, and exclusively at the expense of sickness insurers at one location. At 27 locations, paclitaxel and docetaxel had also been issued in the context of trials, and at 7 locations also via special agreements with the insurers and (or) at the expense of the patient himself. Fifty-three of the 102 taxoid using hospitals had a financial upper limit or a maximum number of patients to be treated. Eighteen of the 102 locations where paclitaxel or docetaxel was issued reported that for financial reasons not all patients eligible for taxoids had been given these drugs. The indications varied from one hospital to another: 67 locations used them for first-phase treatment of patients with ovarian carcinoma, 96 locations for second-phase treatment of patients with ovarian carcinoma and at 91 locations, patients with mammary carcinoma were given taxoids when anthracyclines were no longer indicated. CONCLUSION: Hospitals in 1996 varied greatly with regard to issuing of taxoids. This diversity in part had financial causes. Restrictions on the issuing of taxoids for financial reasons lead to unequal access to care.