bluuebunny/crossref_metadata_2025 huggingface dataset:
Growth and population size of crayfish in headwater streams: individual‐ and higher‐level consequences of acidification
Authors: Seiler Steven M. , Turner Andrew M.
Published: June 2004

1. Environmental stress may have indirect positive effects on population size through modification of food‐web interactions, despite having negative effects on individuals. Here we evaluate the individual‐ and population‐level effects of acidification on crayfish (Cambarus bartonii) in headwater streams of the Allegheny Plateau (PA, U.S.A.) with field experiments and survey data. Median baseflow pH of 24 study reaches in nine streams varied from 4.4 to 7.4, with substantial variation found both among and within streams.

2. Two bioassays were conducted to evaluate the relationship between stream pH and crayfish growth rates. Growth rates were always higher in circumneutral reaches than in acidic reaches. Crayfish originating in acidic water grew less when transplanted into neutral water than did crayfish originating in neutral water, providing some evidence for a cost of acclimation to acidity.

3. Stream surveys showed that fish were less abundant and crayfish more abundant in acidified streams than in circumneutral streams. Crayfish density was sixfold higher in reaches with the lowest pH relative to circumneutral reaches. Large crayfish made up a higher proportion of crayfish populations at sites with high fish biomass, consistent with the hypothesis that fish predation on small individuals may be limiting crayfish population size at these sites.

4. Although individual crayfish suffered lower growth in acidified streams, increased acidity appeared to cause an increase in crayfish population size and shifts in size structure, possibly by relieving predation pressure by fish.
Carp (Cyprinus carpio) as a powerful invader in Australian waterways
Authors: Koehn John D.
Published: June 2004

1. The invasion of carp (Cyprinus carpio L.) in Australia illustrates how quickly an introduced fish species can spread and dominate fish communities. This species has become the most abundant large freshwater fish in south‐east Australia, now distributed over more than 1 million km2.

2. Carp exhibit most of the traits predicted for a successful invasive fish species. In addition, degradation of aquatic environments in south‐east Australia has given them a relative advantage over native species.

3. Derivation of relative measures of 13 species‐specific attributes allowed a quantitative comparison between carp and abundant native fish species across five major Australian drainage divisions. In four of six geographical regions analysed, carp differed clearly from native species in their behaviour, resource use and population dynamics.

4. Climate matching was used to predict future range expansion of carp in Australia. All Australian surface waters appear to be climatically suitable for carp.

5. This assessment strongly reinforces the need for immediate management of carp in Australia to include targeted control of human‐assisted dispersal, such as use of carp as bait by anglers, distribution to new locations by anglers and the use of the ‘Koi’ strain in the aquarium industry.

6. Given their historical spread, dispersal mechanisms and ecological requirements, the expansion of carp across most of the remainder of Australia is to be expected.
Relative influence of bioturbation and predation on organic matter processing in river sediments: a microcosm experiment
Authors: Mermillod‐Blondin Florian , Gaudet Jean‐Paul , Gerino Magali , Desrosiers Gaston , Jose Jacques , Châtelliers Michel Creuzé des
Published: June 2004

1. Our objective was to measure the effects of bioturbation and predation on the physical characteristics and biogeochemical processes in river sediments.

2. We investigated the impacts of tubificid worms tested separately and together with an omnivore (Gammarus pulex), which does feed on tubificids, on sediment distribution, water flux, sediment organic carbon, biofilm biomass and microbial activities, and the concentrations of dissolved oxygen, dissolved organic carbon, PO, NO, NO and NH in slow filtration sand–gravel columns. We hypothesised that gammarids, which exploit the top 2–3 cm of the sediment, would modify the impact of worms at the sediment surface.

3. In experiments both with and without gammarids, bioturbation by the tubificids modified both the distribution of surface particles in the sediment column and water flux. In addition, microbial aerobic (oxygen consumption) and anaerobic (denitrification and fermentative decomposition of organic matter) processes in the sediment were stimulated in the presence of tubificid worms. However, G. pulex did not affect either the density or bioturbation activity of the tubificid worms.

4. Bioturbation by the benthos can be a major process in river habitats, contributing to the retention of organic matter in sediment dynamics. The presence of at least one predator had no effect on bioturbation in sediments. In such systems, physical heterogeneity may be sufficient for tubificids to escape from generalist predators, though more specialised ones might have more effect.
Evidence of coprophagy in freshwater zooplankton
Authors: Pilati Alberto , Wurtsbaugh Wayne. A. , Brindza Nathaniel R.
Published: June 2004

1. Vertical transport of nutrients in sedimenting faecal material is greatly reduced by coprophageous organisms. Unfortunately, nearly all work on faecal production, sedimentation and coprophagy has dealt with copepods in marine ecosystems. Here, we report the first evidence of coprophagy in freshwater zooplankton from oligotrophic and eutrophic lakes. We used 14C‐labelled algae and faecal material to estimate the rates of algal clearance and coprophagy.

2. Measured feeding rates per individual on faecal material were similar (Daphnia pulex, D. rosea, Leptodiaptomus tyrelli) or even higher (D. lumholtzi) than filtering rates on phytoplankton. This finding does not necessarily implicate active selection of faeces over algae because: (i) we did not use the same food concentrations for faeces and algae, and (ii) grazers of slightly different sizes were used in each test.

3. Weight‐specific clearance rates of L. tyrelli and Holopedium gibberum on faecal matter (0.084–0.089 mL μg−1 h−1) were higher than in the daphniids (0.026 mL μg−1 h−1).

4. The data indicate that coprophagy in freshwater ecosystems is an important mechanism of nutrient recycling, and this process should be taken into account when studying nutrient fluxes within lakes and reservoirs.
Retention and supply of zebra mussel larvae in a large river system: importance of an upstream lake
Authors: Stoeckel J. A. , Rehmann C. R. , Schneider D. W. , Padilla D. K.
Published: June 2004

1. Persistence of zebra mussel populations in river systems probably depends upon the presence of upriver sites capable of hosting self‐recruiting adult populations that act as sources of larvae. In this paper we examine the importance of Lake Pepin, a natural riverine lake in the Upper Mississippi River, as an upriver source of larvae to the downstream populations of zebra mussels.

2. Field studies and modelling suggest that Lake Pepin plays a major role in maintaining zebra mussel populations in the Upper Mississippi River. Long water residence times in Lake Pepin allow for self‐recruitment under the right hydraulic conditions. Larval abundance was low to absent upstream of the lake but increased dramatically downriver in all 3 years of the study. Travel time estimates in the Upper Mississippi River show that newly fertilised larvae drifting out of Lake Pepin can contribute substantially to the major downstream peak in larval abundance. In contrast, backwater and other off‐channel sites are unlikely to drive main‐channel abundance patterns. Larval abundances in off‐channel sites were less than or equal to those in the main channel.

3. A key factor in assessing the importance of Lake Pepin as a source population was the abundance of early stage, unshelled larvae. Studies that consider only abundances of older shelled stages (visible by cross polarised lighting) may yield misleading results. Results of this study suggest that efforts to control zebra mussels in the Upper Mississippi River should focus on controlling adult populations within Lake Pepin and reducing or eliminating larvae exiting the lake.
Summer use of a small stream by fish and crayfish and exchanges with adjacent lentic macrohabitats
Authors: Cossette Claudia , Rodríguez Marco A.
Published: June 2004

1. Movements between a stream reach and two adjacent lentic macrohabitats, a beaver pond and a lake, were followed for the Appalachian crayfish and two fish species, brook charr and brown bullhead, over an 85‐d period from early June to late August, and were analysed in relation to water level, maximum water temperature, photoperiod length, lunar luminosity, and age, by use of time‐series regressions.

2. Brook charr showed strong net immigration to the stream reach for underyearling (age class 0+) fish but net emigration for 1+ fish. Both immigration and emigration were positively related to water level and temperature; migratory responses to temperature were age‐specific.

3. Brown bullhead used the stream primarily as a corridor for downstream migration from the beaver pond to the lake. As with brook charr, water level and temperature had a positive effect on movement and responses were stronger in younger individuals.

4. Crayfish emigrated from the stream during the summer. Movements were positively related to increases in water level and temperature, with responses of 1+ crayfish much stronger than those of older individuals.

5. The results indicate that the stream tributary played different roles for brook charr (nursery), brown bullhead (dispersal corridor) and Appalachian crayfish (early summer refuge), and suggest that variation in water level or temperature resulting from climatic change or local anthropogenic activities might modify connectivity between macrohabitats, particularly for younger individuals.
Flow extremes and benthic organic matter shape the metabolism of a headwater Mediterranean stream
Authors: Acuña Vicenç , Giorgi Adonis , Muñoz Isabel , Uehlinger Urs , Sabater Sergi
Published: June 2004

1. Single‐station diel oxygen curves were used to monitor the oxygen metabolism of an intermittent, forested third‐order stream (Fuirosos) in the Mediterranean area, over a period of 22 months. Ecosystem respiration (ER) and gross primary production (GPP) were estimated and related to organic matter inputs and photosynthetically active radiation (PAR) in order to understand the effect of the riparian forest on stream metabolism.

2. Annual ER was 1690 g O2 m−2 year−1 and annual GPP was 275 g O2 m−2 year−1. Fuirosos was therefore a heterotrophic stream, with P : R ratios averaging 0.16.

3. GPP rates were relatively low, ranging from 0.05 to 1.9 g O2 m−2 day−1. The maximum values of GPP occurred during a few weeks in spring, and ended when the riparian canopy was fully closed. The phenology of the riparian vegetation was an important determinant of light availability, and consequently, of GPP.

4. On a daily scale, light and temperature were the most important factors governing the shape of photosynthesis–irradiance (P–I) curves. Several patterns could be generalised in the P–I relationships. Hysteresis‐type curves were characteristic of late autumn and winter. Light saturation responses (that occurred at irradiances higher than 90 μE m−2 s−1) were characteristic of early spring. Linear responses occurred during late spring, summer and early autumn when there was no evidence of light saturation.

5. Rates of ER were high when compared with analogous streams, ranging from 0.4 to 32 g O2 m−2 day−1. ER was highest in autumn 2001, when organic matter accumulations on the streambed were extremely high. By contrast, the higher discharge in autumn 2002 prevented these accumulations and caused lower ER. The Mediterranean climate, and in its effect the hydrological regime, were mainly responsible for the temporal variation in benthic organic matter, and consequently of ER.
Silencing of ribosomal protein L3 genes in N. tabacum reveals coordinate expression and significant alterations in plant growth, development and ribosome biogenesis
Authors: Popescu Sorina C. , Tumer Nilgun E.
Published: June 2004

The expression of ribosomal protein genes is coordinately regulated in bacteria, yeast, and vertebrates, so that equimolar amounts of ribosomal proteins accumulate for assembly into ribosomes. To understand how expression of ribosomal protein genes is regulated in plants, we altered expression of the large subunit ribosomal protein L3 (RPL3) genes in Nicotiana tabacum using post‐transcriptional gene silencing (PTGS). L3 is encoded by two genes, RPL3A and RPL3B, with 80.2% amino acid sequence identity in tobacco. Two types of ‘hairpin’ RNA (hpRNA) vectors carrying the RPL3A or RPL3B sequences in both sense and antisense orientation were generated in order to alter the expression level of both RPL3 genes. Tobacco plants transformed with a vector containing a 5′‐terminal fragment of RPL3A gene displayed decreased RPL3A mRNA levels and a marked increase in the abundance of RPL3B mRNA. These results indicated that expression of the RPL3 genes is coordinately regulated in tobacco. The transgenic plants that contained higher levels of RPL3B mRNA exhibited leaf overgrowth and mottling. Epidermal cells of these plants were increased in number and decreased in size. The precursor rRNA (pre‐rRNA) and the mature rRNAs accumulated in these plants, suggesting that ribosome biogenesis is upregulated. Tobacco plants transformed with an hpRNA vector harboring the full‐length RPL3B cDNA exhibited efficient silencing of both RPL3A and RPL3B genes, reduced L3 levels, and an abnormal phenotype characterized by a delay in development, stunting, and inhibition of lateral root growth. L3 deficiency led to a reduction in cell number and an increase in cell size, suggesting that L3 positively regulates cell division. Decreasing RPL3 gene expression resulted in a decrease in accumulation of the pre‐rRNA, establishing a prominent role for L3 in ribosome biogenesis in plants.
Phosphatidic acid accumulation is an early response in theCf‐4/Avr4interaction
Authors: De Jong Camiel F. , Laxalt Ana M. , Bargmann Bastiaan O. R. , De Wit Pierre J. G. M. , Joosten Matthieu H. A. J. , Munnik Teun
Published: June 2004

TheCladosporium fulvum(Cf)‐4gene of tomato confers resistance to the fungusC. fulvum, expressing the corresponding avirulence (Avr)4gene, which codes for an elicitor protein. Little is known about how such mechanisms work, but previous studies have shown that elicitor recognition activates Ca2+signalling and protein kinases, such as mitogen‐activated protein kinase (MAPK) and calcium‐dependent protein kinase (CDPK). Here, we provide evidence that a new signalling component, the lipid second messenger phosphatidic acid (PA), is produced within a few minutes of AVR4/Cf‐4 interaction. Using transgenic tobacco cells expressing the tomatoCf‐4‐resistance gene as a model system, phospholipid signalling pathways were studied by pre‐labelling the cells with32Piand assaying for the formation of lipid signals after challenge with the fungal elicitor AVR4. A dramatic rapid response was an increase in32P‐PA, together with its metabolic product diacylglycerol pyrophosphate (DGPP). AVR4 increased the levels of PA and DGPP in aCf‐4+‐, time‐ and dose‐dependent manner, while the non‐matching elicitor AVR9 did not trigger any response. In general, PA signalling can be triggered by two different pathways: via phospholipase D (PLD), which generates PA directly by hydrolysing structural phospholipids like phosphatidylcholine (PC), or via PLC, which generates diacylglycerol (DAG) that is subsequently phosphorylated to PA by DAG kinase (DGK). To determine the origin of the AVR4‐induced PA formation, a PLD‐specific transphosphatidylation assay and a differential32P‐labelling protocol were used. The results clearly demonstrated that most PA was produced via the phosphorylation of DAG. Neomycin and U73122, inhibitors of PLC activity, inhibited AVR4‐induced PA accumulation, suggesting that the increase in DGK activity was because of increased PLC activity producing DAG. Lastly, evidence is provided that PLC signalling and, in particular, PA production could play a role in triggering responses, such as the AVR4‐induced oxidative burst. For example, PLC inhibitors inhibited the oxidative burst, and when PA was added to cells, an oxidative burst was induced.
Characterization of C‐terminal domains of Arabidopsis heat stress transcription factors (Hsfs) and identification of a new signature combination of plant class A Hsfs with AHA and NES motifs essential for activator function and intracellular localization
Authors: Kotak Sachin , Port Markus , Ganguli Arnab , Bicker Frank , Von Koskull‐Döring Pascal
Published: June 2004

Heat stress transcription factors (Hsfs) are the major regulators of the plant heat stress (hs) response. Sequencing of the Arabidopsis genome revealed the existence of 21 open‐reading frames (ORFs) encoding putative Hsfs assigned to classes A–C. Here we present results of a functional genomics approach to the Arabidopsis Hsf family focused on the analysis of their C‐terminal domains (CTDs) harboring conserved modules for their function as transcription factors and their intracellular localization. Using reporter assays in tobacco protoplasts and yeast as well as glutathione‐S‐transferase (GST) pull‐down assays, we demonstrate that short peptide motifs enriched with aromatic and large hydrophobic amino acid (aa) residues embedded in an acidic surrounding (AHA motifs) are essential for transcriptional activity of class A Hsfs. In contrast to this, class B and C Hsfs lack AHA motifs and have no activator function on their own. We also provide evidence for the function of a leucine (Leu)‐rich region centered around a conserved QMGΦL motif at the very C‐terminus as a nuclear export signal (NES) of class A Hsfs. Sequence comparison indicates that the combination of a C‐terminal AHA motif with the consensus sequence FWxxF/L,F/I/L as well as the adjacent NES represents a signature domain for plant class A Hsfs, which allowed to identify more than 60 new Hsfs from the expressed sequence tag (EST) database.
Arabidopsis thaliana AtPOLK encodes a DinB‐like DNA polymerase that extends mispaired primer termini and is highly expressed in a variety of tissues
Authors: García‐Ortiz Maria Victoria , Ariza Rafael R. , Hoffman Peter D. , Hays John B. , Roldán‐Arjona Teresa
Published: June 2004

Cell survival after DNA damage depends on specialized DNA polymerases able to perform DNA synthesis on imperfect templates. Most of these enzymes belong to the recently discovered Y‐family of DNA polymerases, none of which has been previously described in plants. We report here the isolation, functional characterization and expression analysis of a plant representative of the Y‐family. This polymerase, which we have termed AtPolκ, is a homolog of Escherichia coli pol IV and human pol κ, and thus belongs to the DinB subfamily. We purified AtPolκ and found a template‐directed DNA polymerase, endowed with limited processivity that is able to extend primer–terminal mispairs. The activity and processivity of AtPolκ are enhanced markedly upon deletion of 193 amino acids (aa) from its carboxy (C)‐terminal domain. Loss of this region also affects the nucleotide selectivity of the enzyme, leading to the incorporation of both dCTP and dTTP opposite A in the template. We detected three cDNA forms, which result from the alternative splicing of AtPOLK mRNA and have distinct patterns of expression in different plant organs. Histochemical localization of β‐glucuronidase (GUS) activity in transgenic plants revealed that the AtPOLK promoter is active in endoreduplicating cells, suggesting a possible role during consecutive DNA replication cycles in the absence of mitosis.
The promotion of gravitropism in Arabidopsis roots upon actin disruption is coupled with the extended alkalinization of the columella cytoplasm and a persistent lateral auxin gradient
Authors: Hou Guichuan , Kramer Victoria L. , Wang Yuh‐Shuh , Chen Rujin , Perbal Gerald , Gilroy Simon , Blancaflor Elison B.
Published: June 2004

The actin cytoskeleton has been implicated in regulating plant gravitropism. However, its precise role in this process remains uncertain. We have shown previously that disruption of the actin cytoskeleton with Latrunculin B (Lat B) strongly promoted gravitropism in maize roots. These effects were most evident on a clinostat as curvature that would exceed 90° despite short periods of horizontal stimulation. To probe further the cellular mechanisms underlying these enhanced gravity responses, we extended our studies to roots of Arabidopsis. Similar to our observations in other plant species, Lat B enhanced the response of Arabidopsis roots to gravity. Lat B (100 nm) and a stimulation time of 5–10 min were sufficient to induce enhanced bending responses during clinorotation. Lat B (100 nm) disrupted the fine actin filament network in different regions of the root and altered the dynamics of amyloplasts in the columella but did not inhibit the gravity‐induced alkalinization of the columella cytoplasm. However, the duration of the alkalinization response during continuous gravistimulation was extended in Lat B‐treated roots. Indirect visualization of auxin redistribution using the DR5:β‐glucuronidase (DR5:GUS) auxin‐responsive reporter showed that the enhanced curvature of Lat B‐treated roots during clinorotation was accompanied by a persistent lateral auxin gradient. Blocking the gravity‐induced alkalinization of the columella cytoplasm with caged protons reduced Lat B‐induced curvature and the development of the lateral auxin gradient. Our data indicate that the actin cytoskeleton is unnecessary for the initial perception of gravity but likely acts to downregulate gravitropism by continuously resetting the gravitropic‐signaling system.
Interactions of tobacco microtubule‐associated protein MAP65‐1b with microtubules
Authors: Wicker‐Planquart Catherine , Stoppin‐Mellet Virginie , Blanchoin Laurent , Vantard Marylin
Published: June 2004

Tobacco microtubule associated protein (MAP65) (NtMAP65s) constitute a family of microtubule‐associated proteins with apparent molecular weight around 65 kDa that collectively induce microtubule bundling and promote microtubule assembly in vitro. They are associated with most of the tobacco microtubule arrays in situ. Recently, three NtMAP65s belonging to the NtMAP65‐1 subfamily have been cloned. Here we investigated in vitro the biochemical properties of one member of this family, the tobacco NtMAP65‐1b. We demonstrated that recombinant NtMAP65‐1b is a microtubule‐binding and a microtubule‐bundling protein. NtMAP65‐1b has no effect on microtubule polymerization rate and binds microtubules with an estimated equilibrium constant of dissociation (Kd) of 0.57 µm. Binding of NtMAP65‐1b to microtubules occurs through the carboxy‐terminus of tubulin, as NtMAP65‐1b was no longer able to bind subtilisin‐digested tubulin. In vitro, NtMAP65‐1b stabilizes microtubules against depolymerization induced by cold, but not against katanin‐induced destabilization. The biological implications of these results are discussed.
Feline corneal sequestra: a review of 64 cases (80 eyes) from 1993 to 2000
Authors: Featherstone Heidi J. , Sansom Jane
Published: June 2004

Feline corneal sequestrum is a common condition of the feline cornea. The purpose of this study was to provide a detailed description of the clinical features of the condition including the response to different management options and to assess the rate of recurrence. The medical records of 64 cases (80 eyes) of feline corneal sequestra that presented to the Animal Health Trust from 1993 to 2000 were reviewed. Fifty‐two cases were reviewed retrospectively; 12 cases were assessed prospectively between April and September 2000 as part of a separate study. The Persian was the most frequently encountered breed and the mean age of affected cats was 5.6 years. At initial presentation, sequestra were unilateral in 58 cats and bilateral in 6 cats, 5 of which were Persians. Ocular discomfort and ocular discharge were common presenting signs, occurring in 42 and 36 eyes, respectively. Seventy‐four eyes were managed surgically with keratectomy only (n = 44) or keratectomy followed by a graft procedure (n = 30). Sequestra recurred in 16 eyes in the study. There was no significant difference in the rate of recurrence between eyes that received a graft procedure (n = 5) and eyes that did not (n = 11) (P = 0.56). Complications following transection of conjunctival pedicle grafts were observed. Brown to black discoloration of noncorneal tissue and therapeutic biomaterials was observed, including discoloration of both viable and apparently nonviable grafted conjunctival tissue, small intestinal submucosa graft material and bandage contact lenses.
Feline corneal sequestrum: laboratory analysis of ocular samples from 12 cats
Authors: Featherstone Heidi J. , Franklin Valerie J. , Sansom Jane
Published: June 2004

Feline corneal sequestrum is a common ocular condition typified by brown to black discoloration of the cornea. The nature of the discoloration has not been identified. The purpose of this study was to perform a laboratory investigation of ocular samples from 12 clinical cases of feline corneal sequestrum in an attempt to characterize the nature of the discoloration. The 12 cases were referred to the Ophthalmology Unit at the Animal Health Trust between April and September 2000, and were also part of a clinical review of 64 cases of feline corneal sequestrum described separately. Five laboratory techniques that are routinely performed at the Biomaterials Unit, Aston University were employed for analysis of the ocular samples. Ocular material included corneal sequestrum, tear samples, meibomian gland secretions, and bandage contact lenses from the 12 clinical cases. High‐performance liquid chromatography data showed that total tear lipid in affected eyes was significantly lower than in control eyes (P = 0.016); total tear lipid in affected eyes was lower than in the unaffected, contralateral eyes of the same cat but the difference was not significant (P = 0.29). The presence of an unknown lipid class was observed in tears and meibomian secretions of affected, contralateral and control eyes. Scanning electron microscopy showed that the discoloration in affected corneas was not due to the presence of iron. Fluorescence spectroscopic analysis of sequestra, unaffected corneas and contact lenses (from affected and contralateral/unaffected eyes) showed that lipid and protein were present but did not play an important role in sequestra. Ultraviolet–visible light absorbance spectroscopy revealed a peak at 385 nm in unaffected corneas that was absent in sequestra and the difference was significant (P < 0.0001); this peak may be a characteristic feature of the normal feline cornea. The absorbance spectra displayed a peak at 280 nm in two sequestra suggesting that chromophore groups (e.g. melanin) were present. Optical microscopy performed on 10 sequestra revealed the presence of particles, which were consistent with the appearance of melanin particles, providing laboratory evidence that characterized the nature of the discoloration as melanin for the first time.
Tick‐borne encephalitis virus as a possible cause of optic neuritis in a dog
Authors: Stadtbäumer K. , Leschnik M. W. , Nell B.
Published: June 2004

A 3‐year‐old spayed female Siberian Husky was presented due to acute vision loss. Examination revealed bilateral optic neuritis and lymphocytic meningoencephalitis. The serum (1:800) and cerebrospinal fluid (CSF; 1:200) immunoglobulin (Ig)G titers for tick‐borne encephalitis virus (TBEV) were elevated as were the serum IgG titer forAnaplasma phagocytophilum(1:640) and serum IgM titer forToxoplasma gondii(1:20). Intracytoplasmic inclusion bodies such as ehrlichial or anaplasmal morulae were not observed in the CSF or blood smear. The dog was treated with methylprednisone and doxycycline. The left eye regained vision; the right eye remained blind. Anti‐inflammatory therapy was stopped on day 18 after diagnosis. Four days later the dog showed evidence of hyperesthesia in the cervical region. Analysis of CSF showed no abnormalities and CSF IgG titers for TBEV andA. phagocytophilumwere negative. Funduscopic evidence of active papillitis was absent on day 22 in the left eye and on day 86 in the right eye. On day 243, the dog was presented again with lethargy, ataxia, disorientation and temporary head tilt. The IgG titer for TBEV was again elevated in the CSF (1:800) and in serum (1:400). After interpretation of all findings, we assume that meningoencephalitis and optic neuritis in this patient was caused by TBEV and associated immune‐mediated inflammation. In endemic areas, TBEV should be considered as cause of optic neuritis in dogs.
Secondary glaucomas in the dog in North America
Authors: Gelatt Kirk N. , MacKay Edward O.
Published: June 2004

Objective To determine the prevalence of secondary glaucomas in dogs associated with cataract formation, lens luxation or displacement, cataract surgery, uveitis, hyphema and intraocular neoplasia.

Methods Information was obtained from the Veterinary Medical Data Base (VMDB) from all veterinary medical teaching hospitals in North America from March 1964 to March 2003. Secondary glaucomas were diagnosed at the same examination or after the primary diagnosis was made, and included those associated with cataract formation, lens luxation, cataract surgery, uveitis of unknown cause, hyphema of unknown cause, and intraocular neoplasia. The data were evaluated by decade, breed, gender and age of presentation.

Results A total of 1 592 831 dogs were presented, and 9695 canine secondary glaucomas. Secondary glaucoma associated with cataract formation represented 81% of all the canine secondary glaucomas. Breeds (n = 7890 dogs) predisposed to secondary glaucoma and cataracts had an overall prevalence of 0.5%, but nearly 20% of all the cataractous dogs developed secondary glaucoma in at least one eye. For the years 1994–2003, these breeds included the American Cocker Spaniel; Boston Terrier; Toy, Miniature and Standard Poodle; English Springer Spaniel; Bichon Frise; and Labrador Retriever. The other forms of secondary glaucoma occurred less frequently, and included those glaucomas with lens luxation or displacement (779 dogs; 12.0%), postcataract surgery (528 dogs; 5.1%), with uveitis from unknown cause (399 dogs; 7.1%), with hyphema from unknown cause (117 dogs; 7.3%), and with intraocular neoplasia (19 dogs; 3.5%). The risk of the secondary glaucomas from 1984 to 2002 was highest after the intracapsular lens extraction (ICLE), less in the extracapsular technique (ECLE), and lowest for the phacoemulsification/phacofragmentation method.

Conclusion Prevalence of the canine secondary glaucomas ranges from 0.25% (1964–1973), 0.46% (1974–1983), 0.79% (1984–1993), to 0.80% (1994–2003) and are as frequent as the primary or breed‐related glaucomas during these same time periods.
Tono‐Pen XL®calibration curves for cats, cows and sheep
Authors: Passaglia Christopher L. , Guo Xiaoli , Chen Jie , Troy John B.
Published: June 2004

The objective of this study was to provide calibration curves for correcting intraocular pressure (IOP) measurements obtained using the Tono‐Pen XL®tonometer in cats, cows and sheep. Twelve eyes from 9 cats, 13 eyes from 7 cows, 10 eyes from 5 sheep were used. The anterior chamber of the eye was cannulatedin vivo,in situ(immediately post mortem) orex vivowith a fine needle and IOP was varied from 10 to 90 mmHg in steps of 10 mmHg by adjusting the height of a saline reservoir connected to the needle. For each pressure setting, several readings of IOP were made using the tonometer. The relationship between Tono‐Pen®reading and manometer setting was linear over the full range of measurement. However, the slope of the data regression line deviated significantly from 1 and indicated that the instrument systematically underestimated IOP. For cats the average slope was 0.62 and for cows and sheep it was 0.72 and 0.69, respectively. For the latter animals, the regression line also had a nonzero intercept of ≈ 4.5 mmHg. Similar results were obtained fromin vivoandex vivoeyes and with different Tono‐Pen XL®tonometers. Although developed for use on humans, the Tono‐Pen XL®can provide reproducible and accurate measurement of IOP in cats, cows and sheep when suitably calibrated by manometry. The calibration curves provided here, and by implication those reported for other animals using this tonometer, differ in slope from those measured with earlier models of the Tono‐Pen®. The reproducibility of the curves we obtained implies that they can be used to correct IOP readings from the Tono‐Pen XL®when manometry is not possible.
Evaluation of intraocular pressure in association with cardiovascular parameters in normocapnic dogs anesthetized with sevoflurane and desflurane
Authors: Almeida D. E. , Rezende M. L. , Nunes N. , Laus J. L.
Published: June 2004

The objective of this study was to determine intraocular pressure (IOP) and cardiac changes in normocapnic dogs maintained under controlled ventilation and anesthetized using sevoflurane or desflurane. Sixteen healthy adult mixed‐breed dogs, seven males and nine females, weighing 10–15 kg were used. The dogs were randomly assigned to one of two groups composed of eight animals anesthetized with sevoflurane (SEVO) or desflurane (DESF). In both groups, anesthesia was induced with propofol (10 mg/kg), and neuromuscular blockade was achieved with rocuronium (0.6 mg/kg/h IV). No premedication was given. Ventilation was adjusted to maintain end‐tidal carbon dioxide partial pressure at 35 mmHg. Anesthesia was maintained with 1.5 minimum alveolar concentration (MAC) of sevoflurane or desflurane. In both groups IOP was measured by applanation tonometry (Tono‐Pen) before induction of anesthesia. IOP, mean arterial pressure (MAP), heart rate (HR), cardiac index (CI) and central venous pressure (CVP) were also measured 45 min after the beginning of inhalant anesthesia and then every 20 min for 60 min. A one‐way repeated measures anova was used to compare data within the same group and Student's t‐test was used to assess differences between groups. P < 0.05 was considered statistically significant. Measurements showed normal IOP values in both groups, even though IOP increased significantly from baseline during the use of desflurane. IOP did not differ between groups. CI in the desflurane group was significantly greater than in the sevoflurane group. Sevoflurane and desflurane have no clinically significant effects on IOP, MAP, HR, CI or VCP in the dog.
Modeling the motion of a toy train powered with a time-dependent applied voltage: Educational implementation and analysis
Authors: Wick D. P. , Ramsdell M. W.
Published: June 2004

We describe the motion of an electric toy train engine that is powered by a time-dependent voltage and travels on a horizontal track. Effects such as friction, the electrically induced torque and electromotive force of the motor, resistance, inductance, and applied voltage are investigated to identify the impact of each on the train’s performance. The parameters that describe these effects are experimentally extracted by considering the train’s steady-state motion achieved for a constant applied voltage. An equivalent inertia parameter is obtained from transient velocity and current measurements. These parameters are employed in a numerical solution to predict the train’s velocity and current for a time-dependent applied voltage. The results are compared with measured values for several independent cases. This analysis has been successfully incorporated into an advanced group project for an introductory course in electricity and magnetism and can be adapted to accommodate students at different levels. Its implementation as an alternative to the traditional laboratory experience is discussed and an assessment of its effectiveness is presented based on the Conceptual Survey in Electricity and Magnetism.
Speckle interferometry experiments with a digital photocamera
Authors: Vannoni Maurizio , Molesini Giuseppe
Published: June 2004

We discuss a simple experiment for detecting small deformations by speckle interferometry. The optical setup uses a laser diode for the source together with a lens to expand the laser beam and a beam splitter dividing the beam and illuminating two scattering surfaces. A low-cost, commercial charge coupled device (CCD) photocamera provides images of the two superimposed speckle fields through the beam splitter. We first take a picture with the system at rest, and then take a second one after a deformation is made in a surface. By simple subtraction of the digital pictures, we obtain a fringe pattern that gives us information about the deformation.
Heisenberg indeterminacy and the fine structure constant
Authors: Bedford Donald , Krumm Peter
Published: June 2004

Two elementary connections are drawn between the Heisenberg relations for photons and for electrons and the maximum number of protons in a nucleus that will permit a stable electron orbital.
Relativistic velocity space, Wigner rotation, and Thomas precession
Authors: Rhodes John A. , Semon Mark D.
Published: June 2004

We develop a relativistic velocity space called rapidity space from the single assumption of Lorentz invariance, and use it to visualize and calculate effects resulting from the successive application of non-collinear Lorentz boosts. In particular, we show how rapidity space provides a geometric approach to Wigner rotation and Thomas precession in the same way that space–time provides a geometrical approach to kinematic effects in special relativity.
Gabor’s hologram in a modern perspective
Authors: Repetto L. , Pellistri F. , Piano E. , Pontiggia C.
Published: June 2004

We review Dennis Gabor’s early results in light of more than fifty years of technological achievements, including the advent of CCD cameras and fast computers. By applying digital reading to one of the first holograms, we demonstrate the continuity between the classical technique and the digital implementation. This experiment can be used as a demonstration without needing the instrumentation of an optics laboratory.
On deconvolving spectra
Authors: de Levie Robert
Published: June 2004

A simple method to deconvolve spectra combines aspects of nonlinear least-squares curve fitting and Fourier transformation to reduce the effects of noise. The method fits data to smooth analytical functions, then deconvolves the latter analytically. For example, when the data can be written as a sum of Gaussians gr=ar exp[−(x−cr)2/2br2], and the transfer function as a single Gaussian gt, then the deconvolved signal is the corresponding sum of Gaussians gs, with cs=cr, bs2=br2−bt2, and as=arbr/bs.
Ye olde inertia demonstration
Authors: Caplan George M. , Heald Mark A.
Published: June 2004

A simple quantitative analysis of the classic inertia ball demonstration explains why the lower string may break for “jerks” weaker than those that normally break the upper string, and why both strings may break—first the lower, then the upper.
Impenetrable barriers and canonical quantization
Authors: Garbaczewski Piotr , Karwowski Witold
Published: June 2004

We address an apparent conflict between the traditional canonical quantization framework of quantum theory and spatially restricted quantum dynamics when the translation invariance of an otherwise free quantum system is broken by boundary conditions. By considering the example of a particle in an infinite well, we analyze spectral problems for related confined and global observables. In particular, we show how we can interpret various operators related to trapped particles by not ignoring the rest of the real line that is never occupied by a particle.
Inaccurate use of asymptotic formulas
Authors: Maj Radosław , Mrówczyński Stanisław
Published: June 2004

The asymptotic form of the plane wave decomposition into spherical waves, which is used to express the scattering amplitude in terms of phase shifts, is incorrect. We explain why and show how to circumvent the mathematical inconsistency.
The kinematics of a superball bouncing between two vertical surfaces
Authors: Hefner Brian T.
Published: June 2004

When a superball is thrown so that it bounces between two horizontal parallel surfaces, the ball will bounce from both surfaces and then return to the person who threw it. If the surfaces are vertical and a ball is thrown downward so that it bounces between both surfaces, it also will return to the person who threw it. In the general case of a superball bouncing between two extended vertical surfaces, the ball becomes trapped instead of falling and moves up and down the length of the channel with an oscillation frequency that depends on the ball’s moment of inertia. For this vertical channel the introduction of a tangential coefficient of restitution produces motion that is similar to both a damped harmonic oscillator and a falling body.
Nonholonomic constraints: A test case
Authors: Gatland Ian R.
Published: June 2004

A two-wheeled cart driven by electrostatic forces provides an example of a nonholonomic system with both external forces and torques.
Neutron stars for undergraduates
Authors: Silbar Richard R. , Reddy Sanjay
Published: June 2004

The calculation of the structure of white dwarf and neutron stars is a suitable topic for an undergraduate thesis or an advanced special topics or independent study course. The subject is rich in many different areas of physics, ranging from thermodynamics to quantum statistics to nuclear physics to special and general relativity. The computations for solving the coupled structure differential equations (both Newtonian and general relativistic) can be done using a symbolic computational package. In doing so, students will develop computational skills and learn how to deal with units. Along the way they also will learn some of the physics of equations of state and of degenerate stars.
A model coaxial photonic crystal for studying band structures, dispersion, field localization, and superluminal effects
Authors: Haché Alain , Slimani Abderrahim
Published: June 2004

We use widely available electronic components and discuss a system in which the dispersion relation of a wave propagating in a periodic medium can be studied. Important effects related to periodic media are observed, including the energy band gap, field localization, and superluminal wave packet tunneling.
Analysis of the vacuum cannon
Authors: Ayars Eric , Buchholtz Louis
Published: June 2004

We develop a model for the velocity of a projectile in a vacuum cannon. The theoretical maximum velocity is independent of the vacuum cannon diameter and projectile mass and is significantly lower than the speed of sound. Experimental measurements support the theory as an upper limit.
Understanding and illustrating the atomic origins of friction
Authors: Ringlein James , Robbins Mark O.
Published: June 2004

Recent advances in the understanding of the atomic origins of friction are described and illustrated with simple simulations. Examples of macroscopic and nanometer scale systems that violate Amontons’ laws of friction are discussed. A more general friction relation is motivated and shown to fit data from simple atomic simulations that can be downloaded and modified. The simulations illustrate the fundamental relation between static friction and potential energy, and between kinetic friction and energy dissipation. Conceptual difficulties in understanding how almost all pairs of surfaces lock together in a potential energy minimum are described, and possible resolutions are discussed. We conclude with an explanation of why Amontons’ laws work so well in many macroscopic systems.
TWISTED SUPERSPACE FOR N=D=2 SUPER BF AND YANG–MILLS WITH DIRAC–KÄHLER FERMION MECHANISM
Authors: KATO JUNJI , KAWAMOTO NOBORU , UCHIDA YUKIYA
Published: June 2004

We propose a twisted D=N=2 superspace formalism. The relation between the twisted super charges including the BRST charge, vector and pseudoscalar super charges and the N=2 spinor super charges is established. We claim that this relation is essentially related with the Dirac–Kähler fermion mechanism. We show that a fermionic bilinear form of twisted N=2 chiral and anti-chiral superfields is equivalent to the quantized version of BF theory with the Landau type gauge fixing while a bosonic bilinear form leads to the N=2 Wess–Zumino action. We then construct a Yang–Mills action described by the twisted N=2 chiral and vector superfields, and show that the action is equivalent to the twisted version of the D=N=2 super Yang–Mills action, previously obtained from the quantized generalized topological Yang–Mills action with instanton gauge fixing.
LARGE-N LIMIT OF NONLOCAL 2D GENERALIZED YANG–MILLS THEORIES ON NON-ORIENTABLE SURFACE
Authors: SAAIDI Kh.
Published: June 2004

The large-group behavior of the nonlocal two-dimensional generalized Yang–Mills theories ( nlgYM 2's) on arbitrary closed non-orientable surfaces is investigated. It is shown that all order of ϕ2k model of these theories has third order phase transition only on the projective plane (RP2). Also the phase structure of [Formula: see text] model of nlgYM 2 is studied and it is found that for γ>0, this model has third order phase transition only on RP 2. For γ<0, it has third order phase transition on any closed non-orientable surfaces except RP 2 and Klein bottle.
AN INTRODUCTION TO SUPERSYMMETRIC GAUGE THEORIES AND MATRIX MODELS
Authors: ARGURIO RICCARDO , FERRETTI GABRIELE , HEISE RAINER
Published: June 2004

We give an introduction to the recently-established connection between supersymmetric gauge theories and matrix models. We begin by reviewing previous material that is required in order to follow the latest developments. This includes the superfield formulation of gauge theories, holomorphy, the chiral ring, the Konishi anomaly and the large N limit. We then present both the diagrammatic proof of the connection and the one based on the anomaly. Our discussion is entirely field theoretical and self contained.
LEPTONIC UNIVERSALITY BREAKING IN ϒ DECAYS AS A PROBE OF NEW PHYSICS
Authors: SANCHIS-LOZANO MIGUEL ANGEL
Published: June 2004

In this work, we examine the possible existence of new physics beyond the standard model which could modify the branching fractions of the leptonic (mainly tauonic) decays of bottomonium vector resonances below the [Formula: see text] threshold. The decay width is factorized as the product of two pieces: (a) the probability of an intermediate pseudoscalar color-singlet [Formula: see text] state (coupling to the dominant Fock state of the Upsilon via a magnetic dipole transition) and a soft (undetected) photon; (b) the annihilation width of the [Formula: see text] pair into two leptons, mediated by a non-standard CP-odd Higgs boson of mass about 10 GeV, introducing a quadratic dependence on the lepton mass in the partial width. The process would be unwittingly ascribed to the ϒ leptonic channel thereby (slightly) breaking lepton universality. A possible mixing of the pseudoscalar Higgs and bottomonium resonances is also considered. Finally, several experimental signatures to check out the validity of the conjecture are discussed.
NONCRITICAL STRING LIOUVILLE THEORY AND GEOMETRIC BOOTSTRAP HYPOTHESIS
Authors: HADASZ LESZEK , JASKÓLSKI ZBIGNIEW
Published: June 2004

The applications of the existing Liouville theories for the description of the longitudinal dynamics of noncritical Nambu–Goto string are analyzed. We show that the recently developed DOZZ solution to the Liouville theory leads to the cut singularities in tree string amplitudes. We propose a new version of the Polyakov geometric approach to Liouville theory and formulate its basic consistency condition — the geometric bootstrap equation. Also in this approach the tree amplitudes develop cut singularities.