Mechanical evaluation of a ruptured Swedish adjustable gastric band.

BACKGROUND: Leakage of a laparoscopically placed Swedish adjustable gastric band (SAGB) was observed 2 1/2 years after placement. The band was evaluated for mechanical inaccuracies by a laboratory. METHODS: The ruptured SAGB was investigated microscopically and wall thicknesses were measured. An unused SAGB was tested, both empty and filled, for mechanical deformity after exposure to saline solution. RESULTS: A permanent transformation of the silicone rubber was found, caused by bowing of the device. 2 tears were present at the end of a kink. The mean wall thickness was within acceptable limits. Exposure of the gastric band to saline solution did not cause any sign of permanent deformity of the silicone rubber. CONCLUSION: The rupture of the gastric band did not seem to be caused by a production error. Long-term deformity, in combination with a continuous dynamic load, may increase the risk of tearing. Long-term follow up is recommended for patients treated with this device.

Scan statistics for temporal surveillance for biologic terrorism.

INTRODUCTION: Intentional releases of biologic agents are often designed to maximize casualties before diagnostic detection. To provide earlier warning, syndromic surveillance requires statistical methods that are sensitive to an abrupt increase in syndromes or symptoms associated with such an attack. OBJECTIVES: This study compared two different statistical methods for detecting a relatively abrupt increase in incidence. The methods were based on the number of observations in a moving time window. METHODS: One class of surveillance techniques generates a signal based on values of the generalized likelihood ratio test (GLRT). This surveillance method is relatively well-known and requires simulation, but it is flexible and, by construction, has the appropriate type I error. An alternative surveillance method generates a signal based on the p-values for the conventional scan statistic. This test does not require simulation, complicated formulas, or use of specialized software, but it is based on approximations and thus can overstate or understate the probability of interest. RESULTS: This study compared statistical methods by using brucellosis data collected by CDC. The methods provided qualitatively similar results. CONCLUSIONS: Relatively simple modification of existing software should be considered so that when GLRTs are performed, the appropriate function will be maximized. When a health department has data that indicate an unexpected increase in rates but its staff lack experience with existing software for surveillance based on GLRTs, alternative methods that only require computing Poisson probabilities can be used.

Determination of the antenna heterogeneity of Photosystem II by direct simultaneous fitting of several fluorescence rise curves measured with DCMU at different light intensities.

Several methods for determination of the antenna heterogeneity of Photosystem II from fluorescence rise curves measured with DCMU have been developed so far. Using these methods, two, three or four types of Photosystem II with respect to the antenna heterogeneity were determined. However, the accuracy of some of these methods is under debate. Here, we present a new method for the determination of the antenna heterogeneity of Photosystem II. The method is based on direct simultaneous fitting of several fluorescence rise curves measured with DCMU at different intensities of light excitation. As several curves measured under different light conditions are fitted simultaneously by the same model, reliability and accuracy in determination of model parameters increase. Our method was applied to two plant materials with different structure of the thylakoid membrane: wheat leaves and cells of green alga Chlamydomonas reinhardtii.

Thermoluminescence and fluorescence study of changes in Photosystem II photochemistry in desiccating barley leaves.

An effect of desiccation (a decrease of relative water content from 97% to 10% within 35 h) on Photosystem II was studied in barley leaf segments (Hordeum vulgare L. cv. Akcent) using chlorophyll a fluorescence and thermoluminescence (TL). The O-J-I-P fluorescence induction curve revealed a decrease of F(P) and a slight shift of the J step to a shorter time with no change in its height. The analysis of the fluorescence decline after a saturating light flash revealed an increased portion of slow exponential components with increasing desiccation. The TL bands obtained after excitation by continuous light were situated at about -27 degrees C (Z(v) band - recombination of P680(+)Q(A) (-)), -14 degrees C (A band - S(3)Q(A) (-)), +12 degrees C (B band - S(2/3)Q(B) (-)) and +45 degrees C (C band - TyrD(+)Q(A) (-)). The bands related to the S-states of oxygen evolving complex (A and B) were reduced by desiccation and shifted to higher and lower temperatures, respectively. In accordance with this, the band observed at about +27 degrees C (S(2)Q(B) (-)) after excitation by 1 flash fired at -10 degrees C and band at about +20 degrees C (S(2/3)Q(B) (-)) after 2 flashes decreased with increasing water deficit and shifted to lower temperatures. A new band around 5 degrees C appeared in both regimes of TL excitation for a relative water content of under 42% and was attributed to the Q band (S(2)Q(A) (-)). It is suggested that under desiccation, an inhibition of the formation of S(2)- and S(3)-states in OEC occurred simultaneously with a lowering of electron transport on the acceptor side of PS II. The temperature down-shift of the TL bands obtained after the flash excitation was induced at the initial phases of water stress, indicating a decrease of the activation energy for the S(2/3)Q(B) (-)recombination.

Spectral characterization of chlorophyll fluorescence in barley leaves during linear heating. Analysis of high-temperature fluorescence rise around 60 degrees C.

The spectral characteristics of chlorophyll fluorescence and absorption during linear heating of barley leaves within the range 25-75 degreesC (fluorescence temperature curve, FTC) were studied. Leaves with various content of light harvesting complexes (green, Chl b-less chlorina f2 and intermittent light grown) revealing different types of FTC were used. Differential absorption, emission and excitation spectra documented four characteristic phases of the FTC. The initial two FTC phases (a rise in the 46-49 degreesC region and a subsequent decrease to about 55 degreesC) mostly reflected changes in the fluorescence quantum yield peaking at about 685 nm. A steep second fluorescence rise at 55-61 degreesC was found to originate from a short-wavelength Chl a spectral form (emission maximum at 675 nm) causing a gradual blue shift of the emission spectra. In this temperature range, a clear correspondence of the blue shift in the emission and absorption spectra was found. We suggest that the second fluorescence rise in FTC reflects a weakening of the Chl a-protein interaction in the thylakoid membrane.

Mathematical modelling of 3-(3',4'-dichlorophenyl)-1,1-dimenthylurea action in plant leaves

A mathematical model of the action of a photosystem II herbicide 3-(3',4'-dichlorophenyl)-1, 1-dimenthylurea, DCMU, in plant leaves upon an external application is presented. The diffusion of DCMU in a plant tissue is described with the help of Fick's laws and the following reaction of the herbicide with the QB-binding site of photosystem II by the mass action theory. The model is used for a description of the effect of the herbicide on chlorophyll fluorescence induction (the O-J-I-P curve) measured with spring barley primary leaves submerged in the herbicide solution. The increase of the J step during the herbicide action is ascribed to an increase of the number of photosystem II centres with bound herbicide molecules and malfunctioning in the electron transport to the plastoquinone pool. The experimental data were fitted with the help of the mathematical model. Values of the diffusion coefficient and the second order rate constant of the reaction of the herbicide with photosystem II, obtained by the fitting procedure, are discussed.Copyright 1998 Academic Press Limited

Low and high temperature dependence of minimum F0 and maximum FM chlorophyll fluorescence in vivo

The aim of this paper is to give a global insight into the behaviour of F0 and FM in a wide temperature range from -100 degreesC to 75 degreesC. We show that the F0 increases upon linear freezing, similarly to the widely published increase of the F0 upon linear heating. In contrast to this the FM decreases upon linear heating in the whole temperature range from -100 degreesC to 75 degreesC. A comparison of low and high temperature induced increase of the F0 is presented. Copyright 1998 Elsevier Science B.V.

Matching among multiple random sequences.

In searching for strong homologies between multiple nucleic acid or protein sequences, researchers commonly look at fixed-length segments in common to the sequences. Such homologies form the foundation of segment-based algorithms for multiple alignment of protein sequences. The researcher uses settings of "unusualness of multiple matches" to calibrate the algorithms. In applications where a researcher has found a multiple matching word, statistical significance helps gauge the unusualness of the observed match. Previous approximations for the unusualness of multiple matches are based on large sample theory, and are sometimes quite inaccurate. Section 2 illustrates this inaccuracy, and provides accurate approximations for the probability of a common word in R out of R sequences. Section 3 generalizes the approximation to multiple matching in R out of S sequences. Section 4 describes a more complex approximation that incorporates exact probabilities and yields excellent accuracy; this approximation is useful for checking the simpler approximations over a range of values.

Chlorophyll fluorescence changes at high temperatures induced by linear heating of greening barley leaves.

A relative decrease of the high temperature part (above 60°C) of the chlorophyll fluorescence temperature curve during 3 h to 10 h greening period of barley (Hordeum vulgare L.) leaves was found to be concomitant to a decrease of Chl alb ratio and to a gradual increase of LHCP/core ratio found by electrophoresis and the ratio of granal to total length of thylakoid membranes. It is suggested that the high temperature part of the fluorescence temperature curve depends inversely on the relative amount of LHC II in thylakoid membranes.

Pattern matching between two non-aligned random sequences.

Given two independent sequences of letters, we seek the probability distribution of the length of the longest matching word. This word can be in different positions in the two sequences and we consider both perfect and nearly perfect matching. We derive bounds and approximations for the probability and compare them with other bounds and approximations. The results can be applied to DNA sequences in molecular biology and generalized matching between two independent random sequences.

Sensitivity of the relative Fpl level of chlorophyll fluorescence induction in leaves to the heat stress.

The (Fpl-Fo)/Fv value of the fluorescence induction curve is shown to be a more suitable parameter to detect a wider range of heat stress damage to thylakoid membranes as compared to quantities t 1/2 (time of fluorescence rise from Fo to (Fo+Fm)/2 level) and % MathType!MTEF!2!1!+-% feaafiart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr% 4rNCHbGeaGak0Jf9crFfpeea0xh9v8qiW7rqqrFfpeea0xe9Lq-Jc9% vqaqpepm0xbba9pwe9Q8fs0-yqaqpepae9pg0FirpepeKkFr0xfr-x% fr-xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaWaa0aaaeaacq% aHepaDaaaaaa!39D5!\[\overline \tau \] (the fluorescence induction time defined as the area above the induction curve normalized to Fv=1). A method for exact and automatic Fpl determination is presented.A break point in the quality and behaviour of the fluorescence induction curve of barley leaves incubated at 49°C was reached at the moment (about 240 s) when the transformation of PS II active (QB-reducing) to PS II inactive (QB-non-reducing) centres was completed. The meaning of the standard Fv and Fv/Fm parameter was then changed.The method of Fpl determination described here may help to increase the analytical value of the standard chlorophyll fluorometers.

Model studies of chlorophyll fluorescence reabsorption at chloroplast level under different exciting conditions.

A theoretical model is presented describing the distortion of chlorophyll fluorescence spectra of a chloroplast or a group of chloroplasts by the effect of fluorescence reabsorption. Model calculations using the experimental data show that the primary reabsorption effect occurs already within one chloroplast and the spectral distortion depends significantly on the excitation regime of the chloroplast. A theoretical dependence of the distortion function, defined as a change in the F(685)/F(735) fluorescence band ratio, on the mean chlorophyll concentration in a chloroplast is predicted for different light excitation regimes. The distortion of measured chlorophyll fluorescence spectra at 77 K of chloroplast suspension adsorbed on filter papers of two strongly different diffusive reflectivities and at different mean chlorophyll concentrations are discussed with the help of the presented theory.

Power of the scan statistic for detection of clustering.

The scan statistic is the maximum number of events in an interval of fixed length w as the subinterval moves over the entire time frame. Previous research derived the null distribution of the scan statistic under the conditional model which assumed that the total number of events was fixed, and under the unconditional model which let the total number of events be a random variable. This paper derives approximations for the power of the scan test for a pulse alternative. Under this alternative, the relative risk of disease on a subinterval (tau, tau + w), tau unknown, is theta-fold as high as it is for other subintervals of length w. Two sets of approximations are given for each model. The first approximation gives highly accurate results, but requires use of a personal computer. The second procedure can be performed on a hand-held calculator and appears very accurate for the cases examined.

The clinical features of children with malrotation of the intestine.

A review was performed of the 37 cases of malrotation of the intestine which occurred in previously healthy children during a 12-year period. There were 33 patients (89%) younger than eight weeks of age, with 17 patients (46%) aged less than one week. Symptoms included bilious vomiting in 36 patients (97%) and constipation in 33 patients (89%). On initial examination, 35 patients (95%) appeared to be well (including 23/25 patients [92%] with volvulus of the midgut), and 28 patients (76%) exhibited no abnormal physical findings on abdominal examination (including 15/25 patients [60%] with volvulus of the midgut). In all, 25 cases (68%) of malrotation were accompanied by volvulus of the midgut; in 21 of these cases, torsion of the bowel was greater than or equal to 360 degrees. There were four patients (11%) with gangrenous bowel requiring surgical resection. The mortality rate associated with this disorder was 5%; both patients who died were neonates with volvulus who presented in shock and had extensively gangrenous bowel. Malrotation of the intestine usually presents in the young infant, is almost always associated with bilious vomiting, and is commonly accompanied by few if any abnormal physical findings suggestive of a serious underlying intraabdominal disease process. An emergent radiographic contrast study of the upper gastrointestinal tract should be performed to delineate the anatomy of the proximal bowel in all young infants with bilious vomiting.

Temporal clustering of homicide among urban 15- to 24-year-old white and black Americans.

Temporal clustering of homicides among 15- to 24-year-old black and white Americans was studied in 22 heavily urbanized counties in the United States from 1979 through 1985. Thirty-eight million people, including 37% of black Americans and 14% of white Americans, lived in these densely developed countries. The pattern of white male homicide deaths was cyclical--that is, statistically significant excesses were observed on weekends and on national holidays. The pattern of black male homicide deaths was much less cyclical. But homicide deaths of black males were disproportionately likely to occur in a pattern of single days with multiple homicides as well as in periodic spikes, lasting less than a week, during which many homicides occurred. Implications for research and policy are discussed.

Rapid method for estimating the risk of acutely controversial side effects of prescription drugs.

When controversy suddenly erupts about the risk of using a prescription drug, there is an urgent need for fast methods of risk estimation. Some unexpected side-effects of prescription drugs are indications for the prescribing of another kind of drug. If the risk of such a side-effect is high, it should be reflected in clustered prescribing of the side-effect-alleviating drug in sequence with the side-effect-causing drug. The risk of drug-attributable side-effects can be estimated by comparing average incidences of initial prescriptions for the side-effect-alleviating drug before, during, and long after the dispensing of the presumed side-effect-causing drug. We monitored computerized, complete drug dispensing records of anonymous outpatients for use of flunarizine, an anti-vertigo/anti-migraine drug that case reports had suggested causes mental depression and/or Parkinsonism. Among 1284 patients who eventually got flunarizine during a 31 month period, 1 in 7 was started on an anti-depressant before or long after flunarizine; only 1 in 82 might be said to have been started on an anti-depressant because of flunarizine. There was no evidence that anti-Parkinson drugs were started because of flunarizine, though the numbers are small. The analysis takes only a few days, and can help set bounds on risks of the subset of adverse drug reactions that are themselves indications for use of other drugs.

Prescription sequence analysis: a new and fast method for assessing certain adverse reactions of prescription drugs in large populations.

Prescription sequence analysis (PSA) uses pharmacy-based prescription drug histories to detect a subset of drug effects: those that are themselves indications for changes in the prescribing of another drug. Dutch pharmacy practice ensures virtually complete drug histories. With a database of 25,000 patients, we used PSA to test an alleged link between the use of the anti-vertigo drug flunarizine and mental depression. The temporal sequence of anti-depressant use among flunarizine users shows no clustering that would suggest a causal link. PSA can be run within a few days, which may make it helpful in resolving certain of the periodic controversies about adverse drug reactions.