bluuebunny/crossref_metadata_2025_split huggingface dataset:
Theoretical studies of the hydrolysis reaction of 5′‐AMP
Authors: Zhang Aihua , Li Lan , Sun Shujuan , Li Zonghe 
Published: January 2006

AbstractThe hydrolysis reaction mechanisms of the phosphate group, with and without an adenosine connected to it, have been theoretically investigated at the B3LYP/6‐31G** level. It is found that each reaction is single‐channel with a two‐step process. When H2O approaches the phosphate group, a penta‐coordinated intermediate (IM1‐a) is formed first, followed by the H transfer reaction with PO broken at the same time. This process belongs to the addition‐elimination process, similar to the carboxylate. In addition, the solvent effect has been studied by the polarizable continuum model (PCM). Our present calculations have rationalized and verified all the possible reaction channels. © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2006
Periodane—An unexpectedly stable molecule of unique composition
Authors: Krüger Thomas 
Published: January 2006

AbstractStructure, bonding characteristics, and reaction energies as well as optical, vibrational, and nuclear magnetic resonance (NMR) properties of the hitherto unknown molecule LiBeBCNOF, called periodane, have been calculated by quantum chemical methods. It can be shown that periodane is stable enough to be produced and identified experimentally. © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2006
TOF‐SIMS studies of yttria‐stabilised zirconia
Authors: Hansen Karin Vels , Norrman Kion , Mogensen Mogens 
Published: January 2006

AbstractThe surface of an as‐polished and an as‐sintered yttria‐stabilised zirconia pellet was analysed with XPS and TOF‐SIMS (depth profiling and imaging) in order to study the distribution of impurities. The polished sample was slightly contaminated with Na, K, Mg and Ca. The sintered sample showed a thin surface film of segregated species, especially Na, Si and Al. Below the surface film, it was found that the grain boundaries were filled with impurities. The chemical compositions of the as‐polished and as‐sintered surfaces are very different and the surface state should be considered when performing electrochemical measurements. Copyright © 2006 John Wiley & Sons, Ltd.
Modelling competing risks in cancer studies
Authors: Klein John P. 
Published: January 2006

AbstractCompeting risks arise commonly in the analysis of cancer studies. Most common are the competing risks of relapse and death in remission. These two risks are the primary reason that patients fail treatment. In most medical papers the effects of covariates on the three outcomes (relapse, death in remission and treatment failure) are model by distinct proportional hazards regression models. Since the hazards of relapse and death in remission must add to that of treatment failure, we argue that this model leads to internal inconsistencies. We argue that additive models for either the hazard rates or the cumulative incidence functions are more natural and that these models properly partition the effect of a covariate on treatment failure into its component parts. We illustrate the use and interpretation of additive models for the hazard rate or for the cumulative incidence function using data from a study of the efficacy of two preparative regimes for hematopoietic stem cell transplantation. Copyright © 2006 John Wiley & Sons, Ltd.
The Manchester operation for uterine prolapse
Authors: Ayhan A. , Esin S. , Guven S. , Salman C. , Ozyuncu O. 
Published: January 2006

AbstractObjectiveTo evaluate the clinical characteristics, complications, and satisfaction scores of patients who underwent the Manchester operation.MethodsThis retrospective observational study evaluated data from 204 women who underwent the Manchester operation at the Department of Obstetrics and Gynecology of Hacettepe University School of Medicine, Ankara, Turkey, from January 1985 to April 2004.ResultsMean age was 34.68 ± 4.24 years and parity 2.47 ± 0.96; 85.8% of the patients were premenopausal; 176 patients (86.28%) had grade 3 and 28 (13.72%) had grade 2 uterine prolapse; 95.1% of the patients had associated cystoceles and 51.3% had associated rectoceles; and 81.4% had urinary incontinence. Regarding early postoperative complications, 27 patients (13.23%) had febrile morbidity; retroperitoneal hematoma occurred in 1 patient (0.49%); urinary retention occurred in 45 patients (22.05%), and cervical stenosis occurred in 23 patients (11.27%). At 1 year, 1 patient had undergone abdominal hysterectomy because of unsuccessful cervical dilatation; and a mean of 3.6 years following the operation, 8 patients (3.9%) had undergone the tension‐free vaginal tape procedure plus a vaginal hysterectomy for recurrent stress urinary incontinence and uterine prolapse. The mean satisfaction/acceptance score for the operation was 8.52 ± 2.13 (range, 2–10).ConclusionA high degree of acceptance/satisfaction and a low morbidity rate show the Manchester operation to be a good option for the treatment of uterine prolapse in women who wish to keep their uterus.
Abrupt climate change: An alternative view
Authors: Wunsch Carl 
Published: January 2006

AbstractHypotheses and inferences concerning the nature of abrupt climate change, exemplified by the Dansgaard–Oeschger (D–O) events, are reviewed. There is little concrete evidence that these events are more than a regional Greenland phenomenon. The partial coherence of ice core δ18O and CH4 is a possible exception. Claims, however, of D–O presence in most remote locations cannot be distinguished from the hypothesis that many regions are just exhibiting temporal variability in climate proxies with approximately similar frequency content. Further suggestions that D–O events in Greenland are generated by shifts in the North Atlantic ocean circulation seem highly implausible, given the weak contribution of the high latitude ocean to the meridional flux of heat. A more likely scenario is that changes in the ocean circulation are a consequence of wind shifts. The disappearance of D–O events in the Holocene coincides with the disappearance also of the Laurentide and Fennoscandian ice sheets. It is thus suggested that D–O events are a consequence of interactions of the windfield with the continental ice sheets and that better understanding of the wind field in the glacial periods is the highest priority. Wind fields are capable of great volatility and very rapid global-scale teleconnections, and they are efficient generators of oceanic circulation changes and (more speculatively) of multiple states relative to great ice sheets. Connection of D–O events to the possibility of modern abrupt climate change rests on a very weak chain of assumptions.
The effects of host physiology on the attraction of tsetse (Diptera: Glossinidae) andStomoxys(Diptera: Muscidae) to cattle
Authors: Torr S.J. , Mangwiro T.N.C. , Hall D.R. 
Published: January 2006

AbstractIn Zimbabwe, studies were made of the numbers of tsetse (Glossinaspp.) and stable flies (Stomoxysspp.) attracted to cattle of different nutritional status, age and sex. Host odours were analysed to determine the physiological basis of these differences and improved methods are described for measuring rates of production of kairomones. Seasonal fluctuations in host weight, related to changes in pasture quality, had no significant effect on attraction of tsetse orStomoxys. However, both attraction to different individuals and carbon dioxide production by these individuals were strongly correlated with weight, suggesting a possible link. Attraction to the odour from different types of cattle decreased in the order ox > cow > heifer > calf, and oxen were twice as attractive as calves of less than 12 months old. Lactation did not alter the relative attractiveness of cows. Calves less than six months old produced lower levels of carbon dioxide, acetone, octenol and phenols than oxen, but for older calves and cows, levels of production of known kairomones and repellents were similar to those of an ox. Carbon dioxide produced by cattle varied according to time of day and the animal's weight; cattle weighing 500 kg produced carbon dioxide at a mean rate of 2.0 l min−1in the morning and 2.8 l min−1in the afternoon compared to respective rates of 1.1 and 1.9 l min−1for cattle weighing 250 kg. Artificially adjusting the doses of carbon dioxide produced by individual cattle to make them equivalent did not remove significant differences in attractiveness for tsetse but did forStomoxys. Increasing the dose of carbon dioxide from 1 to 4 l min−1in a synthetic blend of identified kairomones simulating those produced by a single ox, increased attractiveness to tsetse but not to the level of an ox. The results suggest that the main sources of differences in the attractiveness of individual cattle are likely to be variation in the production of carbon dioxide and, for tsetse, other unidentified kairomone(s). The biological and practical implications of these findings are discussed.
Avoiding the projective hierarchy in expansions of the real field by sequences
Authors: Miller Chris 
Published: January 2006

Some necessary conditions are given on infinitely oscillating real functions and infinite discrete sets of real numbers so that first-order expansions of the field of real numbers by such functions or sets do not define

N

\mathbb N

. In particular, let

f
:

R

→

R

f\colon \mathbb R\to \mathbb R

be such that

lim

x
→
+
∞

f
(
x
)
=
+
∞

\lim _{x\to +\infty }f(x)=+\infty

,

f
(
x
)
=
O
(

e

x
N

)

f(x)=O(e^{x^N})

as

x
→
+
∞

x\to +\infty

for some

N
∈

N

N\in \mathbb N

,

(

R

,
+
,
⋅
,
f
)

(\mathbb R, +,\cdot ,f)

is o-minimal, and the expansion of

(

R

,
+
,
⋅
)

(\mathbb R,+,\cdot )

by the set

{

f
(
k
)
:
k
∈

N

}

\{\,f(k):k\in \mathbb {N}\,\}

does not define

N

\mathbb N

. Then there exist

r
>
0

r>0

and

P
∈

R

[
x
]

P\in \mathbb R[x]

such that

f
(
x
)
=

e

P
(
x
)

(
1
+
O
(

e

−
r
x

)
)

f(x)=e^{P(x)}(1+O(e^{-rx}))

as

x
→
+
∞

x\to +\infty

.
The interrelation of the size of fish eggs, the date of spawning and the production cycle
Authors: Bagenal T. B. 
Published: January 2006

The variability in size of pelagic and demersal marine and freshwater fish eggs is examined. The difference between the smallest and largest volumes, based on published figures for the diameters, is large in many species. In marine species with planktonic eggs, the median percentage difference is just over 100%, and this is similar in species with demersal eggs and in freshwater fish.The available evidence suggests that geographical differences in egg size are small, but in marine fish there is a well‐known seasonal decline in egg size. In herring it has previously been shown that egg size in different spawning groups can be correlated with the timing of the production cycle. A similar correlation can be seen in the seasonal shift in time and locality of spawning, and egg size, of the plaice. Sufficient data on seasonal freshwater fish egg variations are not available, but the time of spawning does appear to be linked with the availability of food for the larvae in both lake and stream species.
Environmental control of teleost reproductive cycles: a brief review
Authors: de Vlaming Victor L. 
Published: January 2006

Reports concerned with the environmental regulation of teleost reproductive cycles are critically reviewed. Photoperiod and temperature have been the most frequently studied environmental factors with respect to control of sexual cycling. Photoperiod may exert the dominant regulatory role in the salmonid family, but few species have been examined so no conclusive statement is presently possible. Both photoperiod and temperature may be important controlling factors in the cyprinid family, but inadequate controls prohibit meaningful interpretation. Temperature may be extremely important in regulating reproductive cycles in the cyprinodontiform fishes. Although the data are inconclusive, it appears that changes in daylength play some role in reproductive cycling in the gasterosteids. Photoperiod and temperature seem to interact in regulating the sexual cycles in the 2 periform species investigated.It is concluded that short term laboratory studies may lead to erroneous statements concerning the importance of exogenous factors in controlling annual reproductive cycles. Although photoperiod has been credited as the dominant environmental regulatory factor in many previous investigations, photoperiodism seems to be temperature sensitive in a majority of the teleost species studied. Responsiveness to exogenous factors appears to depend on the gonadal condition of the beginning controls (effects vary with season). Considerable variation is seen in the reproductive timing mechanisms among the teleosts and few generalizations can be made with regard to phylogenetic, geographic or ecological relationships of the fishes studied.
Revised food consumption estimate of a bluegill sunfish population in Wyland Lake, Indiana, U.S.A.
Authors: Gerking Shelby D. 
Published: January 2006

The estimate of food consumption by the bluegill sunfish (Lepomis macrochirus) population of Wyland Lake, Indiana, was examined with reference to recent research on the length of the growing season and the effect of body weight, ration and activity on growth efficiency. Growth efficiency was measured in the laboratory in terms of protein, comparing nitrogen assimilated with nitrogen accumulated over a period of about 30 days.The revised consumption of protein was 134.9kg (or 1407kg live weight of aquatic organisms, 444 kg/ha) during a growing season of 111 days compared with the original estimate of 127.3 kg calculated for an assumed growing season of 150 days, a difference of only 6%. The correspondence between the two estimates was coincidental. The original estimate was made at a time when the growing season had not been measured and the effect of ration and body size on growth efficiency was not precisely known. Corrections for these factors plus that for activity compensated for one another, closely approaching, by chance, the original value.
Biochemical genetics of the Atlantic salmon Salmo salar L.
Authors: Wilkins Noël P. 
Published: January 2006

In recent years, blood group and protein polymorphisms in Atlantic salmon have been investigated extensively with a view, primarily, to their use in identifying individuals of different spawning populations present in high seas fisheries. Erythrocyte antigens, haemoglobins, serum proteins and various tissue enzymes—mainly esterases and de‐hydrogenases—have been studied by electrophoretic and immunological techniques. These studies are reviewed here for the first time.Many of the protein systems exhibit multiple components and this fact, together with cytological evidence, indicates the occurrence of tetraploidy in the course of Salmonid evolution. The significance of a tetraploid origin in the evolution and ecological adaptation of Salmonids is discussed briefly.Some protein systems studied exhibit phylogenetic variation, and analyses of phenotype ratios and allele frequencies indicate that the populations of different river systems are genetically distinct. Allele frequencies have not yet been shown to be stable from generation to generation however, and some of the factors likely to affect allele frequencies are discussed.Different spawning populations can not be identified in high seas fisheries using these protein characters, although it may be possible to identify the continent of origin (N. America or Europe) of some individuals. Indeed, it has been proposed independently by two groups that North American and European populations of Atlantic salmon be assigned to different sub‐species viz. S. s. americanus and S. s. europaeus respectively. The contradictory evidence on which these taxa are proposed is discussed, together with the evidence for other population groups proposed in the European part of the salmon's range. The possible role and future direction of studies on the biochemical genetics of salmon are outlined.
Observations on the age, growth, reproduction and food of the dace, Leuciscus leuciscus (L.), in two rivers in southern England
Authors: Mann R. H. K. 
Published: January 2006

Scales of 497 dace from the river Stour and 573 from the river Frome were used for age determinations. Annuli were laid down in late May to early June at the start of the growth period. Minimal growth occurred from November to April. Male dace grew minimally faster than females; Frome dace faster than those from the Stour. Growth rates in the two rivers were similar to those published for most other European waters. Variation in growth rates in different years was not great, but there were marked differences in recruitment success. Spawning occurred in the second half of March and elaboration of the gonads between September and March. Immature dace have an annual cycle in condition with a maximum in June and a minimum during the winter months. The condition of the mature females is affected by the gonad cycle. The fecundity of Stour dace is represented by the formula:
image
and for Frome dace by:
image
Most dace were mature by age IV, but there were more mature II and III group fish in the Frome population. Molluscs and Trichoptera larvae comprised the bulk of the winter diet of Stour dace, and Ephemeroptera nymphs, Simulium and chironomid larvae were the principal constituents during the summer.
Ecological notes on the Haplochromis (Pisces: Cichlidae) species‐flock of Lake George, Uganda (East Africa)
Authors: Dunn I. G. 
Published: January 2006

Lake George, a shallow equatorial lake, supports a Haplochromis species‐flock of 17 species. Of the five species that dominate the species‐flock, two feed mainly on benthic and mid‐water dipteran larvae, one is a piscivore, one exploits microcrustacea and another the abundant blue‐green phytoplankton population. There is little stenophagy in this group. There is a seasonal variation in the total gill‐net catch of the three dominant Haplochromis of the sandy shoal habitat, with high catches in ths wet season and low catches in the dry. Similar fluctuations are known to occur in the commercial catches of Sarotherodon niloticus. No seasonal changes were observed in the proportions of the individual species making up this community and the individuals breed all the year round.A combination of ecologically unspeeialized species, resulting in an efficient exploitation and stability of the ecosystem may account for the observed high fish biomass and the high numbers of individuals. Taking into account the effect of the monotony of the environmental conditions, the physical continuty of the available habitat types and the relatively short time that the lake has been in existence, coupled with the apparent lack of rigid ecological requirements by the individual members of the Haplochromis group, it is suggested that this species‐flock may still be at an early stage in its evolutionary develoment.
Experiments on the resistance of fish to rapid increase in hydrostatic pressure
Authors: Lampert Winfried 
Published: January 2006

In a few hydro‐electric pumping stations in the southern Black Forest it has been found that fish occurring in the high lying reservoirs could only arrive there from the river below after an upward transport through the pumping system. As there is a height difference of 400 m to overcome the fish must withstand a sudden pressure change of 40 atm. To test whether this is actually possible various species of fish were subjected suddenly to a pressure of 50 atm which was then reduced to 1 atm over a period of 10 min.No mortality occurred. Although the pressure shock symptoms exhibited by the different species of fish were variable, all appeared to be perfectly normal 2 h after the experiment.
Distribution, reproduction and growth of the catfish, Chrysichthys walkeri (Gunther) in the Lekki Lagoon, Nigeria
Authors: Ikusemiju Kola 
Published: January 2006

An investigation was made on the biology of the catfish, Chrysichthys walkeri (Gunther) occurring in the Lekki Lagoon. The catfish was evenly distributed over the six sampled stations of the lagoon with the sites of the shallow water stations probably serving both as breeding and nursery grounds.Fecundity estimates for this species ranged from 896 to 4168 eggs. The average number of eggs per female was 2084. Laboratory incubated eggs hatched after 3 days with the yolk sac being completely absorbed on the seventh day. The fry averaged 8.6 mm on their first day of life.The catfish attained a maximum total length of 25.7 cm within a period of 2 years. There were no significant differences in the growth pattern of this species during the dry and rainy seasons.
The basis of food selection in flounders, Platichthys flesus (L.), in the Severn Estuary
Authors: Moore J. W. , Moore I. A. 
Published: January 2006

The factors influencing the selection of food by flounders, Platichthys flesus (L.), have been investigated by analysing collections made in the Severn Estuary for 1 year and the results of experiments. Flounders measuring between 6–0 and 35 cm fed heavily on the polychaete Nereis diversicolor in February and on the amphipod Gammarus salinus between February and April. Thereafter these species were replaced by the mysid Neomysis integer with the decapod Crangon vulgaris. Flounders shorter than 6.0 cm, fed mainly on Neomysis integer regardless of month. Numerous factors were involved in the choice of the food including (1) the maximum and minimum length of prey, (2) its spatial distribution in the water column, (3) its degree of concealment, (4) its motility and ability to escape predation, (5) conditioning of the flounders for certain foods, (6) the fish's swimming speed and (7) the turbidity and temperature of the water.Although the average length of ingested prey remained unchanged as the fish grew in size, an increase in the maximum and minimum lengths was observed. The percentage of stomachs that contained no identifiable remains in flounders greater than 6–0 cm averaged 80–95 % during part of the winter and 60% in the summer and between January and March. These changes partly reflected the influence of low water temperature on the metabolic rate and availability of prey. The dry weight of the stomach contents in flounders longer than 6–0 cm was lowest in winter but high values were recorded in the spring. This latter feature was probably because the rate of feeding was greater than that of digestion. During the summer, under more normal feeding conditions, the weight of the stomach contents remained relatively low compared to other fish populations. Flounders shorter than 6–0 cm always contained more food in their stomachs on a unit weight basis than larger individuals, reflecting metabolic rate and hunting efficiency.
A trypanosome from the plaice, Pleuronectes platessa L.
Authors: Cottrell B. J. 
Published: January 2006

The results of a 12 month study of Trypanosoma platessae Lebailly (1904), a haemoflagellate parasitising the plaice, Pleuronectes platessa L., are presented. The morphological features of the trypanosome are described, with experimental investigations of the host specificity of T, platessae. The flagellate occurred at low parasitaemias in wild plaice with a seasonal variation in the numbers of infected hosts, the percentage of parasitised fish reaching a maximum of 20 % in March and declining in the summer months.Attempts to establish T. platessae in the laboratory, by means of passage of infected blood, gave inconsistent results. Elevated levels of β‐globulins were detected in the sera of T. platessae infected plaice, and it is suggested that this may be associated with antibody secretion to the parasite.