bluuebunny/crossref_metadata_2025 huggingface dataset:
Using Chimeric Hypoviruses To Fine-Tune the Interaction between a Pathogenic Fungus and Its Plant Host
Authors: Chen Baoshan , Geletka Lynn M. , Nuss Donald L.
Published: July 2002

Infectious cDNA clones of mild (CHV1-Euro7) and severe (CHV1-EP713) hypovirus strains responsible for virulence attenuation (hypovirulence) of the chestnut blight fungus
Cryphonectria parasitica
were used to construct viable chimeric viruses. Differences in virus-mediated alterations of fungal colony morphology, growth rate, and canker morphology were mapped to a region of open reading frame B extending from nucleotides 2,363 to 9,904. By swapping domains within this region, it was possible to generate chimeric hypovirus-infected
C. parasitica
isolates that exhibited a spectrum of defined colony and canker morphologies. Several severe strain traits were observed to be dominant. It was also possible to uncouple the severe strain traits of small canker size and suppression of asexual sporulation. For example, fungal isolates infected with a chimera containing nucleotides 2363 through 5310 from CHV1-Euro7 in a CHV1-713 background formed small cankers that were similar in size to that caused by CHV1-EP713-infected isolates but with the capacity for producing asexual spores at levels approaching that observed for fungal isolates infected with the mild strain. These results demonstrate that hypoviruses can be engineered to fine-tune the interaction between a pathogenic fungus and its plant host. The identification of specific hypovirus domains that differentially contribute to canker morphology and sporulation levels also provides considerable utility for continuing efforts to enhance biological control potential by balancing hypovirulence and ecological fitness.
Human Cytomegalovirus Virions Differentially Incorporate Viral and Host Cell RNA during the Assembly Process
Authors: Greijer Astrid E. , Dekkers Chantal A. J. , Middeldorp Jaap M.
Published: July 2002

While analyzing human cytomegalovirus (HCMV) gene expression in infected cells by RNA-specific nucleic acid sequence-based amplification (NASBA), positive results were observed for HCMV RNA encoded by several viral genes immediately after the addition of the virus. UV-inactivated virus also gave a positive NASBA result without establishing active infection, suggesting that RNA was associated with the inoculum. Highly purified virions devoid of cellular contamination proved to be positive for viral RNA encoding both immediate-early (UL123) and late (UL65) gene products. Virion-associated RNA might be incorporated specifically or without selection during the virion assembly. In the latter case, cellular RNA would also be present in the virion. A high-abundant cellular RNA encoded by GAPDH and even U1A RNA, which is expressed at low levels, were detected in the virion fraction, whereas cellular DNA was absent. Virion fractionation revealed that cellular RNA was absent in purified de-enveloped capsids. In conclusion, cellular and viral RNA was present between the capsid and envelope of the virion, whereas in the capsid only viral RNA could be detected. The results suggest that virion-associated viral and cellular RNA is incorporated nonspecifically during virion assembly.
Increased Expression and Immunogenicity of Sequence-Modified Human Immunodeficiency Virus Type 1
gag
Gene
Authors: zur Megede Jan , Chen Min-Chao , Doe Barbara , Schaefer Mary , Greer Catherine E. , Selby Mark , Otten Gillis R. , Barnett Susan W.
Published: July 2002

A major challenge for the next generation of human immunodeficiency virus (HIV) vaccines is the induction of potent, broad, and durable cellular immune responses. The structural protein Gag is highly conserved among the HIV type 1 (HIV-1) gene products and is believed to be an important target for the host cell-mediated immune control of the virus during natural infection. Expression of Gag proteins for vaccines has been hampered by the fact that its expression is dependent on the HIV Rev protein and the Rev-responsive element, the latter located on the
env
transcript. Moreover, the HIV genome employs suboptimal codon usage, which further contributes to the low expression efficiency of viral proteins. In order to achieve high-level Rev-independent expression of the Gag protein, the sequences encoding HIV-1
SF2
p55
Gag
were modified extensively. First, the viral codons were changed to conform to the codon usage of highly expressed human genes, and second, the residual inhibitory sequences were removed. The resulting modified
gag
gene showed increases in p55
Gag
protein expression to levels that ranged from 322- to 966-fold greater than that for the native gene after transient expression of 293 cells. Additional constructs that contained the modified
gag
in combination with modified
protease
coding sequences were made, and these showed high-level Rev-independent expression of p55
Gag
and its cleavage products. Density gradient analysis and electron microscopy further demonstrated that the modified
gag
and
gagprotease
genes efficiently expressed particles with the density and morphology expected for HIV virus-like particles. Mice immunized with DNA plasmids containing the modified
gag
showed Gag-specific antibody and CD8
+
cytotoxic T-lymphocyte (CTL) responses that were inducible at doses of input DNA 100-fold lower than those associated with plasmids containing the native
gag
gene. Most importantly, four of four rhesus monkeys that received two or three immunizations with modified
gag
plasmid DNA demonstrated substantial Gag-specific CTL responses. These results highlight the useful application of modified
gag
expression cassettes for increasing the potency of DNA and other gene delivery vaccine approaches against HIV.
Fatty Acid-Depleted Albumin Induces the Formation of Echovirus A Particles
Authors: Ward Trevor , Powell Robert M. , Chaudhry Yasmin , Meredith Janet , Almond Jeffrey W. , Kraus Werner , Nelsen-Salz Birgit , Eggers Hans J. , Evans David J.
Published: July 2002

Picornavirus infection requires virus uncoating, associated with the production of 135S “A” particles and 80S empty particles from 160S mature virions, to release the RNA genome into the cell cytoplasm. Normal albumin inhibits this process. We now show that when depleted of fatty acids, albumin induces the formation of echovirus A particles.
Functional and Selective Targeting of Adenovirus to High-Affinity Fcγ Receptor I-Positive Cells by Using a Bispecific Hybrid Adapter
Authors: Ebbinghaus Christina , Al-Jaibaji Ahmed , Operschall Elisabeth , Schöffel Angelika , Peter Isabelle , Greber Urs F. , Hemmi Silvio
Published: July 2002

Adenovirus (Ad) efficiently delivers its DNA genome into a variety of cells and tissues, provided that these cells express appropriate receptors, including the coxsackie-adenovirus receptor (CAR), which binds to the terminal knob domain of the viral capsid protein fiber. To render CAR-negative cells susceptible to Ad infection, we have produced a bispecific hybrid adapter protein consisting of the amino-terminal extracellular domain of the human CAR protein (CARex) and the Fc region of the human immunoglobulin G1 protein, comprising the hinge and the CH2 and CH3 regions. CARex-Fc was purified from COS7 cell supernatants and mixed with Ad particles, thus blocking Ad infection of CAR-positive but Fc receptor-negative cells. The functionality of the CARex domain was further confirmed by successful immunization of mice with CARex-Fc followed by selection of a monoclonal anti-human CAR antibody (E1-1), which blocked Ad infection of CAR-positive cells. When mixed with Ad expressing eGFP, CARex-Fc mediated an up to 250-fold increase of transgene expression in CAR-negative human monocytic cell lines expressing the high-affinity Fcγ receptor I (CD64) but not in cells expressing the low-affinity Fcγ receptor II (CD32) or III (CD16). These results open new perspectives for Ad-mediated cancer cell vaccination, including the treatment of acute myeloid leukemia.
Susceptibility of Rat-Derived Cells to Replication by Human Immunodeficiency Virus Type 1
Authors: Keppler Oliver T. , Yonemoto Wesley , Welte Frank J. , Patton Kathryn S. , Iacovides Demetris , Atchison Robert E. , Ngo Tuan , Hirschberg David L. , Speck Roberto F. , Goldsmith Mark A.
Published: July 2002

Progress in developing a small animal model of human immunodeficiency virus type 1 (HIV-1) disease would greatly facilitate studies of transmission, pathogenesis, host immune responses, and antiviral strategies. In this study, we have explored the potential of rats as a susceptible host. In a single replication cycle, rat cell lines Rat2 and Nb2 produced infectious virus at levels 10- to 60-fold lower than those produced by human cells. Rat-derived cells supported substantial levels of early HIV-1 gene expression, which was further enhanced by overexpression of human cyclin T1. Rat cells displayed quantitative, qualitative, and cell-type-specific limitations in the late phase of the HIV-1 replication cycle including relative expression levels of HIV-1 Gag proteins, intracellular Gag processing, and viral egress. Nb2 cells were rendered permissive to HIV-1 R5 viruses by coexpression of human CD4 and CCR5, indicating that the major restriction on HIV-1 replication was at the level of cellular entry. We also found that primary rat lymphocytes, macrophages, and microglia expressed considerable levels of early HIV-1 gene products following infection with pseudotyped HIV-1. Importantly, primary rat macrophages and microglia, but not lymphocytes, also expressed substantial levels of HIV-1 p24 CA and produced infectious virions. Collectively, these results identify the rat as a promising candidate for a transgenic small animal model of HIV-1 infection and highlight pertinent cell-type-specific restrictions that are features of this species.
In Vitro Assembly of Sindbis Virus Core-Like Particles from Cross-Linked Dimers of Truncated and Mutant Capsid Proteins
Authors: Tellinghuisen Timothy L. , Perera Rushika , Kuhn Richard J.
Published: July 2002

A nucleic acid-bound capsid protein dimer was previously identified using a Sindbis virus in vitro nucleocapsid assembly system and cross-linking reagents. Cross-link mapping, in combination with a model of the nucleocapsid core, suggested that this dimer contained one monomer from each of two adjacent capsomeres. This intercapsomere dimer is believed to be the initial intermediate in the nucleocapsid core assembly mechanism. This paper presents the purification of cross-linked dimers of a truncated capsid protein and the partial purification of cross-linked dimers of a full-length assembly-defective mutant. The assembly of core-like particles from these cross-linked capsid protein dimers is demonstrated. Core-like particles generated from cross-linked full-length mutant CP(19-264)L52D were examined by electron microscopy and appeared to have a morphology similar to that of wild-type in vitro-assembled core-like particles, although a slight size difference was often visible. Truncated cross-linked CP(81-264) dimers generated core-like particles as well. These core-like particles could subsequently be disassembled when reversible cross-linking reagents were used to form the dimers. The ability of the covalent intercapsomere cross-link to rescue capsid proteins with assembly defects or truncations in the amino-terminal region of the capsid protein supports the previous model of assembly and suggests a possible role for the amino-terminal region of the protein.
The Initiator Element in a Herpes Simplex Virus Type 1 Late-Gene Promoter Enhances Activation by ICP4, Resulting in Abundant Late-Gene Expression
Authors: Kim Dool-Bboon , Zabierowski Susan , DeLuca Neal A.
Published: July 2002

The start site regions of late genes of herpes simplex virus type 1 are similar to the eukaryotic initiator sequence (Inr), have been shown to affect the levels of expression, and may also play a role in transcription activation by the viral activator ICP4. A series of linker-scanning mutations spanning the start site of transcription and several downstream mutations in the true late gC promoter were analyzed in reconstituted in vitro transcription reactions with and without ICP4, as well as in the context of the viral genome during infection. The nucleotide contacts previously found to be important for Inr function were also found to be important for optimal induction by ICP4. While the Inr had a substantial effect on the accumulation of gC RNA during infection, no other sequence downstream of the TATA box to +124 had a significant effect on levels of expression during infection. Therefore, these studies suggest that TATA box and the Inr are the only
cis
-acting elements required to achieve optimal expression of gC, and that the high levels of late-gene transcription may be largely due to the induction by ICP4, functioning through the Inr element.
Amino-Terminal Precursor Sequence Modulates Canine Distemper Virus Fusion Protein Function
Authors: von Messling Veronika , Cattaneo Roberto
Published: July 2002

The fusion (F) proteins of most paramyxoviruses are classical type I glycoproteins with a short hydrophobic leader sequence closely following the translation initiation codon. The predicted reading frame of the canine distemper virus (CDV) F protein is more complex, with a short hydrophobic sequence beginning 115 codons downstream of the first AUG. To verify if the sequence between the first AUG and the hydrophobic region is translated, we produced a specific antiserum that indeed detected a short-lived F protein precursor that we named PreF
0
. A peptide resulting from PreF
0
cleavage was identified and named Pre, and its half-life was measured to be about 30 min. PreF
0
cleavage was completed before proteolytic activation of F
0
into its F
1
and F
2
subunits by furin. To test the hypothesis that the Pre peptide may influence protein activity, we compared the function of F proteins synthesized with that peptide to that of F proteins synthesized with a shorter amino-terminal signal sequence. F proteins synthesized with the Pre peptide were more stable and less active. Thus, the Pre peptide modulates the function of the CDV F protein. Interestingly, a distinct two-hit activation process has been recently described for human respiratory syncytial virus, another paramyxovirus.
Role of Water in Synthesis of Higher Alcohols from CO and H2 over MoS2
Authors: Andreev Atanas A. , Mintchev Lubomir S. , Gabrovska Margarita V.
Published: July 2002

Experimental evidence was found in support of the direct participation of water in synthesis reactions from CO and hydrogen over MoS2 and K/MoS2 through its dissociation to activated OH and H. A reaction mechanism based on a common formate intermediate in alcohol and hydrocarbon synthesis and water-gas shift reaction is proposed.
Diffusion-Layer Theory for Flows Under Apparent Wall Slip
Authors: Wein Ondřej
Published: July 2002

An explicit analytical formula is given for the overall mass transfer coefficient between the bulk of flowing microdisperse liquid and a small but finite active part of a solid surface. The apparent wall slip effect inside a diffusion layer is reflected through the local power-law velocity profile, vx(z) = Bzp, and a distribution B = B(x,y) over the solid surface.
Steroidal Saponins from Lilium candidum L.
Authors: Haladová Mária , Eisenreichová Eva , Mučaji Pavel , Buděšínský Miloš , Ubik Karel
Published: July 2002

(25S)-3β-{β-D-glucopyranosyl-(1→4)-[α-L-rhamnopyranosyl-(1→2)]-β-D-glucopyranosyloxy}spirost-5-en-27-ol and (25R,26R)-3β-{β-D-glucopyranosyl-(1→4)-[α-L-rhamnopyranosyl-(1→2)]-β-D-glucopyranosyloxy}-26-methoxyspirost-5-ene were isolated from the ethanolic extract of fresh bulbs and petals of Lilium candidum L. Their structures were derived mainly from NMR and mass spectra.
Synthesis of Bis(diphenylphosphinio)octahydro-closo-decaborates L2B10H8 (L = Ph2PH) and 1-(Diphenylphosphinio)nonahydro-closo-decaborates(1-) [1-LB10H9]- (L = Ph2PH, Ph2P(OH)) by the Palladium-Catalyzed Reaction of Ph2PH with 1-Diazononahydro-closo-decaborate(1-) [1-N2B10H9]-
Authors: Naoufal Daoud , Bonnetot Bernard , Mongeot Henri , Grüner Bohumír
Published: July 2002

(PPh3)2PdCl2 and CuI, used in low concentration as catalysts, favour the replacement of the diazo group of [1-N2B10H9]- by Ph2PH. Owing to its instability [1-(Ph2PH)B10H9]- could not be isolated in a pure form and was obtained as a mixture with [1-Ph2P(OH)B10H9]-, but pure samples of [1-Ph2P(OH)B10H9]- were easily obtainable. (PPh3)2PdCl2 also acted as a reactant, the reduction of Pd(II) to Pd(0) allowing the formation of the neutral substituted boranes 1,6-(Ph2PH)2B10H8 and 1,10-(Ph2PH)2B10H8. These two isomers were separated by chromatography. All the products were characterized by 11B and 31P NMR and mass spectrometry techniques.
Chemical Characterization and Synthesis of the Major Component of the Sex Pheromone of the Sugarcane Borer Diatraea saccharalis
Authors: Svatoš Aleš , Kalinová Blanka , Kindl Jiří , Kuldová Jelena , Hovorka Oldřich , Do Nascimento Ruth Rufino , Oldham Neil J.
Published: July 2002

(9Z,11E)-Hexadeca-9,11-dienal (1) was identified as a major component of the sex pheromone of the sugarcane borer Diatraea saccharalis. The identification is based on mass spectral examination of the extracts prepared from calling females, derivatization experiments with 4-methyl-3,5-dihydro-1,2,4-triazole-3,5-dione (2), stereospecific synthesis of dienal 1, and gas chromatography (GC) with electroantennographic detection (GC-EAD). In GC analysis, the antennaly active component and synthetic dienal 1 show identical retention times on several GC phases. However, the behavioral activity of synthetic 1 was much weaker than that of natural extracts. This suggests that an additional component(s) might be involved in sexual communication of this species.
Bone status in cystic fibrosis
Authors: Sood M , Hambleton G , Super M , Fraser W D , Adams J E , Mughal M Z
Published: July 2002

AIM

To investigate bone mineral status of children with cystic fibrosis (CF).

METHODS

In 29 children with CF and 49 matched controls, bone mineral content (BMC), projected bone area (BA), and areal bone mineral density (BMD) of the whole body, total hip, and lumbar spine (L1–L4) were measured using dual energyxray absorptiometry. The BMC values at each site were adjusted for BA, height, and weight. At the lumbar spine, the bone mineral apparent density (BMAD) was calculated by dividing the BMC by the estimated volume, derived from BA. Vertebral (T12–L3) trabecular bone mineral density (vTBMD) was measured using quantitative computed tomography in children with CF. Calcaneal broadband ultrasound attenuation (BUA) was measured in CF patients and controls using quantitative ultrasound. The disease severity of CF children was evaluated by the Shwachman–Kulczycki (SK) score.

RESULTS

The mean BUA, whole body and regional BA, adjusted BMC, and areal BMD of children with CF were not different from those of controls. The mean BMAD of the lumbar spine was reduced in CF patients compared with controls, whereas the mean vTBMD standard deviation scores were significantly higher in CF patients. The median SK score of the CF group was 81 (range 42–100), indicating that as a group our CF patient population had relatively mild disease.

CONCLUSION

The normal vertebral BMC, decreased BMAD, and higher vTBMD suggests that the vertebral cortical thickness or density might be reduced in CF subjects. The overall bone mineral status of CF children with relatively mild disease was not different from size matched controls.
World cup soccer players tend to be born with sun and moon in adjacent zodiacal signs
Authors: Verhulst J
Published: July 2002

The ecliptic elongation of the moon with respect to the sun does not show uniform distribution on the birth dates of the 704 soccer players selected for the 1998 World Cup. However, a uniform distribution is expected on astronomical grounds. The World Cup players show a very pronounced tendency (p = 0.00001) to be born on days when the sun and moon are in adjacent zodiacal signs.
Growth hormone and insulin-like growth factor I in a Sydney Olympic gold medallist: Table 1
Authors: Armanini D , Faggian D , Scaroni C , Plebani M
Published: July 2002

An Italian athlete who won a gold medal at the Sydney Olympic Games was studied. She was accused of doping after the finding of high levels of plasma growth hormone (GH) before the Games. She was studied firstly under stressed and then under unstressed conditions. In the first study, GH was measured every 20 minutes for one hour; it was above the normal range in all blood samples, whereas insulin-like growth factor I (IGF-I) was normal. In the second study, GH progressively returned to accepted normal levels; IGF-I was again normal. It was concluded that the normal range for GH in athletes must be reconsidered for doping purposes, because athletes are subject to stress and thus to wide variations in GH levels.
The epidemiology of hepatitis C in a UK health regional population of 5.12 million
Authors: Mohsen A H , Group Trent HCV Study
Published: July 2002

BACKGROUND

The epidemiology and natural history of hepatitis C virus (HCV) infection in the UK are uncertain. Previous reports are from small or selected populations such as blood donors or tertiary referral centres.

AIMS

To study the epidemiology and natural history of HCV infection.

METHODS

Prospective study incorporating five centres within the Trent region. Patients were managed and followed up according to a commonly agreed protocol.

SUBJECTS

A total of 1128 HCV positive patients. Patients with haemophilia, human immunodeficiency virus, and chronic renal failure were excluded.

RESULTS

Between September 1991 and December 1998, 2546 anti-HCV positive patients were identified of whom 1128 (44%) were enrolled in the cohort. A risk factor(s) for infection was identified in 93.4% of patients who completed the questionnaire; 81% of patients were HCV RNA positive. A total of 397 initial liver biopsies were scored by a single pathologist. These showed a correlation between high alcohol intake and fibrosis score. Multivariate analysis showed fibrosis to be associated with age over 40, past evidence of hepatitis B virus infection, and higher necroinflammatory grade but not with sex, viral genotype, maximum known alcohol intake, estimated duration of infection, or mode of transmission. Twelve (7.8%) of 153 patients who received interferon therapy had sustained serum virus clearance. Sixty six patients have died during the follow up period, 31 with a liver related cause of death. This represents a considerable excess over the expected death rate for a cohort of this age and sex distribution.

CONCLUSIONS

HCV infection is an emerging health problem in the Trent region. Identifying risk factors for infection and disease severity will enhance understanding and facilitate improved intervention. An excess mortality in infected individuals is already evident in this unselected cohort.
Dysphagia and thoracoabdominal aneurysm
Authors: Taylor C W , Sinha A , Nightingale J M D
Published: July 2002

Two elderly patients who presented with gradually progressive dysphagia are described. Investigations excluded an intraluminal obstruction and showed extrinsic compression of the oesophagus by an aneurysmal aorta. Surgery was not performed and they were successfully managed with a liquid diet.
It could only happen to a doctor—Haemophilus aphrophilus septicaemia complicated by a prevertebral infection after dental work
Authors: Poullis A , Gould S R , Lim A G
Published: July 2002

A 53 year old man presented with severe neck pain and a flu-like illness; he had recently returned from Sri Lanka and had had dental treatment six days before illness onset. Blood culture showed infection by Haemophilus aphrophilus. Magnetic resonance imaging was performed and exploratory surgery undertaken. The prevertebral cervical fascia was inflamed but no abscess identified. He was treated with antibiotics and made an uneventful recovery.
Environmental engineering education in Canada
Authors: Smith Daniel W , Biswas N
Published: July 2002

Environmental engineering education has been an active option for engineers from all disciplines for nearly 50 years at the graduate level. Some graduate programs expanded to integrate students with undergraduate science degrees with the engineering programs, since the cross discipline interaction is required outside the academic programs. In the mid-1980s interest increased to such a level that undergraduate programs began to form. Several of these programs have been accredited in their various forms recognizing the diversity of the field and those presenting the programs. The progression from graduate-degree-based specializations to broad-based undergraduate programs reflects both the increased knowledge in the field and the increased demand for professional engineers capable of responding to public health and environmental protection issues. Graduate programs greatly expand fundamental knowledge of physical, chemical, and biological processes and their application to protection problems. Of course, the doctorate is dedicated to the development of significant new knowledge. This paper defines several of the basic components of the environmental engineering profession and the educational process needed to produce qualified environmental engineers. Key words: environmental engineering, education, courses, undergraduate environmental engineering, graduate environmental engineering.
MK801 impairs thermoregulation in the heat
Authors: Canini Frédéric , Simler Nadine , Bourdon Lionel
Published: July 2002

The effects of MK801 (dizocilpine), a glutamate NMDA receptor antagonist, on thermoregulation in the heat were studied in awake rats exposed to 40°C ambient temperature until their body core temperature reached 43°C. Under these conditions, MK801-treated rats exhibited enhanced locomotor activity and a steady rise in body core temperature, which reduced the heat exposure duration required to reach 43°C. Since MK801-treated rats also showed increased striatal dopaminergic metabolism at thermoneutrality, the role of dopamine in the MK801-induced impairment of thermoregulation in the heat was determined using co-treatment with SCH23390, a dopamine D1 receptor antagonist. SCH23390 normalized the locomotor activity in the heat without any effect on the heat exposure duration. These results suggest that the MK801-induced impairment of thermoregulation in the heat is related to neither a dopamine metabolism alteration nor a locomotor activity enhancement.Key words: heatstroke, NMDA receptor, thermoregulation, dopamine, locomotion.
APPROXIMATING THE NEAREST NEIGHBOR INTERCHARGE DISTANCE FOR NON-UNIFORM-DEGREE EVOLUTIONARY TREES
Authors: HON WING-KAI , LAM TAK-WAH
Published: July 2002

The nearest neighbor interchange (nni) distance is a classical metric for measuring the distance (dissimilarity) between evolutionary trees. It has been known that computing the nni distance is NP-complete. Existing approximation algorithms can attain an approximation ratio log n for unweighted trees and 4 log n for weighted trees; yet these algorithms are limited to degree-3 trees. This paper extends the study of nni distance to trees with non-uniform degrees. We formulate the necessary and sufficient conditions for nni transformation and devise more topology-sensitive approximation algorithms to handle trees with non-uniform degrees. The approximation ratios are respectively [Formula: see text] and [Formula: see text] for unweighted and weighted trees, where d ≥ 4 is the maximum degree of the input trees.
GROUP COHOMOLOGY, MODULAR THEORY AND SPACE-TIME SYMMETRIES
Authors: BRUNETTI R. , GUIDO D. , LONGO R.
Published: July 2002

The Bisognano-Wichmann property on the geometric behavior of the modular group of the von Neumann algebras of local observables associated to wedge regions in Quantum Field Theory is shown to provide an intrinsic sufficient criterion for the existence of a covariant action of the (universal covering of) the Poincaré group. In particular this gives, together with our previous results, an intrinsic characterization of positive-energy conformal pre-cosheaves of von Neumann algebras. To this end we adapt to our use Moore theory of central extensions of locally compact groups by polish groups, selecting and making an analysis of a wider class of extensions with natural measurable properties and showing henceforth that the universal covering of the Poincaré group has only trivial central extensions (vanishing of the first and second order cohomology) within our class.
PROBABILITY STRUCTURES FOR QUANTUM STATE SPACES
Authors: BUSCH PAUL , CASSINELLI GIANNI , LAHTI PEKKA J.
Published: July 2002

The theme of this paper is to represent the states of a quantum system by means of probability measures. We fix a positive operator valued measure E on a measurable space (Ω, ℬ(Ω)) acting in a Hilbert space ℋ, and we study the properties of the mapping that it induces from the set of trace class operators on ℋ to the set of measures on (Ω, ℬ(Ω)). In particular, the injectivity and the surjectivity of this map are characterised in terms of the properties of E.
METHODS FOR THE ANALYSIS OF THE LINDSTEDT SERIES FOR KAM TORI AND RENORMALIZABILITY IN CLASSICAL MECHANICS: A review with Some Applications
Authors: GENTILE G. , MASTROPIETRO V.
Published: July 2002

This paper consists in a unified exposition of methods and techniques of the renormalization group approach to quantum field theory applied to classical mechanics, and in a review of results: (1) a proof of the KAM theorem, by studying the perturbative expansion (Lindstedt series) for the formal solution of the equations of motion; (2) a proof of a conjecture by Gallavotti about the renormalizability of isochronous hamiltonians, i.e. the possibility to add a term depending only on the actions in a hamiltonian function not verifying the anisochrony condition so that the resulting hamiltonian is integrable. Such results were obtained first by Eliasson; however the difficulties arising in the study of the perturbative series are very similar to the problems which one has to deal with in quantum field theory, so that the use of the methods which have been envisaged and developed in the last twenty years precisely in order to solve them allows us to obtain unified proofs, both conceptually and technically. In the final part of the review, the original work of Eliasson is analyzed and exposed in detail; its connection with other proofs of the KAM theorem based on his method is elucidated.
SEVERI VARIETIES AND BRANCH CURVES OF ABELIAN SURFACES OF TYPE (1, 3)
Authors: LANGE H. , SERNESI E.
Published: July 2002

A polarized abelian surface (A, L) of type (1, 3) induces a 6:1 covering of A onto the projective plane with branch curve, a plane curve B of degree 18. The main result of the paper is that for a general abelian surface of type (1, 3), the curve B is irreducible and reduced and admits 72 cusps, 36 nodes or tacnodes, each tacnode counting as 2 nodes, 72 flexes and 36 bitangents. The main idea of the proof is that for a general (A, L) the discriminant curve in the linear system |L| coincides with the closure of the Severi variety of curves in |L| admitting a node and is dual to the curve B in the sense of projective geometry.
MAGNETIC PROPERTIES OF NANOCRYSTALLINE NiFe2O4 POWDERS PREPARED BY AN AQUEOUS OXIDATIVE PRECIPITATION PROCESS
Authors: RAJENDRAN M. , BHATTACHARYA A. K. , DAS D. , CHINTALAPUDI S. N. , MAJUMDAR C. K.
Published: July 2002

Nanocrystalline NiFe 2 O 4 powder has been prepared by an oxidative precipitation process at room-temperature and the crystallite size dependent magnetic properties have been studied. The NiFe 2 O 4 powders prepared at room-temperature had an average crystallite size of 6 nm and showed a reduced saturation magnetisation (M s ) of 3 emu · g -1. The crystallite size was increased by heating the samples to increasingly higher temperatures. The M s value increased from 3 to 40 emu·g -1 as the crystallite size was increased from 6 to 120 nm. The samples having crystallite sizes from 6 to 20 nm were superparamagnetic at room-temperature. The Mössbauer spectrum of the 6 nm sized sample showed a broad quadruple doublet, whereas, the 40 nm sized sample showed a clear sextet pattern, with a hyperfine field values of 466 and 504 kOe for A(tetraheral) and B(octahedral) sublattices, respectively. It is shown that the saturation magnetisation and magnetic hyperfine field values are significantly reduced in nanocrystalline NiFe 2 O 4 as a function of crystallite size.
STUDIES OF ELECTRONIC PROPERTIES OF MEDIUM AND LARGE MOLECULES ORIENTED IN A STRONG UNIFORM ELECTRIC FIELD
Authors: KONG WEI
Published: July 2002

Polarization spectroscopy of oriented gas phase medium and large molecules achieved via a uniform DC electric field provides a means to determine the direction of transition dipoles. In this article, the theoretical background of this orientation method, its characterization, and its application in studies of electronic transitions, will be presented. Mature gas phase spectroscopic methods have been developed for studies of small molecules, but studies of medium to large sized species are faced with special challenges. These challenges arise from differences between large and small molecules: large systems typically exhibit fast internal conversion, slow dissociation, and low translational energy release upon dissociation. Thus conventional gas phase spectroscopic techniques are not applicable to derive the direction of the transition dipole. DC induced orientation offers a solution to this problem. It is ideal for studies of systems with small rotational constants and large permanent dipoles, even when a detailed knowledge of the molecular structure, such as the direction of the permanent dipole in the molecular frame, is unknown. The degree of orientation can be calculated using the linear variation method, given the rotational temperature and the size of the permanent dipole. The associated experimental observables can be used to confirm the effect of orientation, or to determine the direction of a transition dipole. These observables include the ratio of excitation probabilities under different polarization directions and spectroscopic features. In some cases, the direction and size of the permanent dipole of the excited electronic state can also be determined. Examples of this type of polarization spectroscopy are presented for asymmetric tops such as diazines, acetelye-HF clusters, nitroaromatics and butyl nitrite. Illustrations of pendular states and its application in linear and diatomic molecules are also briefed. Applications of this method for studies of large molecules and potential pitfalls will be discussed.
LIE ALGEBRA OF THE q-POINCARÉ GROUP AND q-HEISENBERG COMMUTATION RELATIONS
Authors: ASCHIERI PAOLO
Published: July 2002

We discuss quantum orthogonal groups and their real forms. We review the construction of inhomogeneous orthogonal q-groups and their q-Lie algebras. The geometry of the q-Poincaré group naturally induces a well defined q-deformed Heisenberg algebra of hermitian q-Minkowski coordinates xaand momenta pa.
EPR AND MAGNETIC SUSCEPTIBILITY STUDIES OF Cr3+ IONS IN THE 70TeO2 · 25B2O3· 5SrF2 GLASS MATRIX
Authors: ARDELEAN I. , PETEANU M. , IONCU V. , MURESAN N.
Published: July 2002

The chromium ion distribution in x Cr 2 O 3 · (100 - x)[ 70TeO 2 · 25B 2 O 3 · 5SrF 2] glasses with 0 < x ≤ 20 mol% was revealed by EPR and magnetic susceptibility measurements. Cr 3+ ions were detected as the only valence state. Isolated Cr 3+ ions in strongly distorted octahedral symmetric sites as well as associated in exchange coupled pairs were identified, their preponderance depending on the Cr2O3 content of the sample.
CONFIGURATION-DEPENDENT MAGNETISM FROM TWO MANGANESE ATOMS ON Cu(001)
Authors: YANG CHIH-KAI
Published: July 2002

Our calculations, based on first principles, have shown that magnetism from two manganese atoms embedded in the surface layer of Cu(001) depends on their relative positions. If the two Mn atoms are nearest neighbors, the magnetic moment for either atom is only 0.49μB. If separated by one lattice constant, each of the two Mn atoms has a larger moment of 0.66μB and the surrounding Cu atoms also acquire substantial moments. Finally, when a Cu atom is interposed between the two Mn atoms, moment for each Mn atom increases to 3.71μB, about the value of a single Mn impurity in the surface layer. The results indicate that a strong d–d interaction between the Mn and Cu atoms and a weaker interaction between the Mn atoms are behind the shifting of energy levels for the majority and minority spins, which in turn results in very different magnetic moments.
Thermo-Electric Power of High-Tc Oxide Superconductors
Authors: Xiao-Qiang Yang , Li-Yuan Zhang
Published: July 2002

Using the formula of thermo-electric power for the local pair model, based on the two-component model of high-T c superconductivity, we study the experiments of thermo-electric power of several kinds of high-T c oxide superconductors and find that this model can give a general explanation of the thermo-electric power phenomena of high-T c oxide superconductors. According to the study of thermo-electric power of HgBa 2 CuO 4+δ and HgBa 2 CaCu 2 O 6+δ, we consider that the physical properties of underdoped and optimum doped samples are analogous, which are different from overdoped samples. The property of overdoped samples approaches to that of the conventional metal.
X-RAY SMALL-ANGLE REFLECTION AND HIGH-ANGLE DIFFRACTION STUDIES ON Co/Cu MAGNETIC MULTILAYERS
Authors: WU X. S. , BIE Q. S. , LIN Z. S. , HU A. , ZHAI H. R. , JIANG S. S.
Published: July 2002

With varying thickness of the spacer near the second oscillatory GMR peak in Co/Cu system, a series of glass/Fe/[ Co / Cu ]20/ Co multilayers are prepared by magnetronsputtering technique. The MR values are relatively small. High angle X-ray diffraction shows that the copper crystallizes in fcc structure with (111) texture and the cobalt crystallizes in hcp structure with (002) preferential orientation. There is a mixed amorphous CoCu layer at the interface due to the diffusion between cobalt and copper, which may decrease the MR value. The thickness, the mass density for each sub-layer and the surfacial and interfacial roughnesses are refined from the X-ray specular reflectivity measurement.
EFFECT OF A VARIABLE DELAY IN DELAYED DYNAMICAL SYSTEMS
Authors: MADRUGA S. , BOCCALETTI S. , MATÍAS M. A.
Published: July 2002

We report numerical evidence of the effects of a periodic modulation in the delay time of a delayed dynamical system. By referring to a Mackey–Glass equation and by adding a modulation in the delay time, we describe how the solution of the system passes from being chaotic to shadow periodic states. We analyze this transition for both sinusoidal and sawtooth wave modulations, and we give, in the latter case, the relationship between the period of the shadowed orbit and the amplitude of the modulation. Future goals and open questions are highlighted.
PETROV TYPES AND SPECIAL REFERENCE FRAMES
Authors: GEMELLI GIANLUCA , De FELICE FERNANDO , BINI DONATO
Published: July 2002

The Petrov classification is studied with the language of spacetime splitting with respect to a generic timelike unit vector field. Canonical forms of the Weyl tensor for each Petrov type are introduced in terms of preferred reference frames. As an application, the canonical forms of the Bel–Robinson superenergy density and flux are constructed and applications to Bel's definition of gravitational radiation are considered.
A NOTE ON RISKY BOND VALUATION
Authors: HUI C. H. , LO C. F.
Published: July 2002

This paper develops a corporate bond valuation model that incorporates a default barrier with dynamics depending on stochastic interest rates and variance of the corporate bond function. Since the volatility of the firm value affects the level of leverage over time through the variance of the corporate bond function, more realistic default scenarios can be put into the valuation model. When the firm value touches the barrier, bondholders receive an exogenously specified number of riskless bonds. We derive a closed-form solution of the corporate bond price as a function of firm value and a short-term interest rate, with time-dependent model parameters governing the dynamics of the firm value and interest rate. The numerical results show that the dynamics of the barrier has material impact on the term structures of credit spreads. This model provides new insight for future research on risky corporate bonds analysis and modelling credit risk.
CLOSED FORM VALUATION OF AMERICAN BARRIER OPTIONS
Authors: HAUG ESPEN GAARDER
Published: July 2002

Closed form formulae for European barrier options are well known from the literature. This is not the case for American barrier options, for which no closed form formulae have been published. One has therefore had to resort to numerical methods. Lattice models like a binomial or a trinomial tree, for valuation of barrier options are known to converge extremely slowly, compared to plain vanilla options. Methods for improving the algorithms have been described by several authors. However, these are still numerical methods that are quite computer intensive. In this paper we show how some American barrier options can be valued analytically in a very simple way. This speeds up the valuation dramatically as well as give new insight into barrier option valuation.
MOTION MODELING CONCEPTS IN VIRTUAL MANUFACTURING SIMULATOR
Authors: TESIC RADE , BANERJEE PAT
Published: July 2002

Motion modeling is a fundamental component of any virtual manufacturing simulator. Motion modeling tools presented in this paper enable users to have full control of trajectory and motion parameters during entire simulation. Bezier spline based trajectory specification technique is used in modeling complex trajectories. Instead of using computationally expensive numerical analyses routines, a very accurate local technique is used for estimation and derivation of the motion parameters.
STRATEGIC ENVIRONMENTAL ASSESSMENT OF THE INDIA ECODEVELOPMENT PROJECT: EXPERIENCES, PROSPECTS AND LESSONS LEARNT
Authors: RAJVANSHI ASHA
Published: July 2002

The India Ecodevelopment Project (IEP), supported from the Global Environmental Facility (GEF) and International Development Aid (IDA), funds of The World Bank is a major initiative to promote the conservation of biological diversity through the implementation of the ecodevelopment strategies around select Protected Areas (PAs) in India. The environmental review of the IEP became a mandatory requirement for fulfilling the investment eligibility criteria of the donor agencies. Strategic Environmental Assessment (SEA) was applied as an environmental appraisal tool for the evaluation of proposed investment under IEP. The paper discusses the lessons learnt from the application of SEA to IEP in two select PAs viz. Gir National Park and Sanctuary and Ranthambhore Tiger Reserve. SEA led to the identification of the impact potential of some of the activities proposed under IEP. Accordingly, appropriate strategies and feasible alternatives have been suggested for reducing undesirable changes in the ecological, economic and social fabric of the two PAs' environment. The SEA has been undoubtedly recognised as a powerful means to steer the IEP along environmentally sustainable path.
Evaluation of queries in independent database schemes
Authors: Sagiv Yehoshua
Published: July 2002

A simple characterization of independent database schemes is proved. An algorithm is given for translating a tableau
T
, posed as a query on a representative instance, to a union of tableaux that is equivalent to
T
, but can be applied directly to database relations. The algorithm may take exponential time (in the size of
T
and the database scheme), and it is applicable only to independent database schemes. If
T
is a just a projection of a representative instance, then the algorithm has a simpler form (which is still exponential in the worst case) and is polynomial in some cases.
Safety and translation of relational calculus
Authors: Van Gelder Allen , Topor Rodney W.
Published: July 2002

Not all queries in relational calculus can be answered sensibly when disjunction, negation, and universal quantification are allowed. The class of relation calculus queries or formulas that have sensible answers is called the
domain independent
class which is known to be undecidable. Subsequent research has focused on identifying large decidable subclasses of domain independent formulas. In this paper we investigate the properties of two such classes: the
evaluable
formulas and the
allowed
formulas. Although both classes have been defined before, we give simplified definitions, present short proofs of their main properties, and describe a method to incorporate equality.

Although evaluable queries have sensible answers, it is not straightforward to compute them efficiently or correctly. We introduce
relational algebra normal form
for formulas from which form the correct translation into relational algebra is trivial. We give algorithms to transform an evaluable formula into an equivalent
allowed
formula and from there into relational algebra normal form. Our algorithms avoid use of the so-called
Dom
relation, consisting of all constants appearing in the database or the query.

Finally, we describe a restriction under which every domain independent formula is evaluable and argue that the class of evaluable formulas is the largest decidable subclass of the domain independent formulas that can be efficiently recognized.
A file system for continuous media
Authors: Anderson David P. , Osawa Yoshitomo , Govindan Ramesh
Published: July 2002

The Continuous Media File System, CMFS, supports real-time storage and retrieval of continuous media data (digital audio and video) on disk. CMFS clients read or write files in “sessions,” each with a guaranteed minimum data rate. Multiple sessions, perhaps with different rates, and non-real-time access can proceed concurrently. CMFS addresses several interrelated design issues; real-time semantics fo sessions, disk layout, an acceptance test for new sessions, and disk scheduling policy. We use simulation to compare different design choices.
Solving queries by tree projections
Authors: Sagiv Yehoshua , Shmueli Oded
Published: July 2002

Suppose a database schema
D
is extended to
D¯
by adding new relation schemas, and states for
D
are extended to states for
D¯
by applying joins and projections to existing relations. It is shown that certain desirable properties that
D¯
has with respect to
D
. These properties amount to the ability to compute efficiently the join of all relations in a state for
D
from an extension of this state over
D¯
. The equivalence is proved for unrestricted (i.e., both finite and infinite) databases. If
D¯
is obtained from
D
by adding a set of new relation schemas that form a tree schema, then the equivalence also holds for finite databases. In this case there is also a polynomial time algorithm for testing the existence of a tree projection of
D¯
with respect to
D
.
Altruistic locking
Authors: Salem Kenneth , García-Molina Héctor , Shands Jeannie
Published: July 2002

Long-lived transactions (LLTs) hold on to database resources for relatively long periods of time, significantly delaying the completion of shorter and more common transactions. To alleviate this problem we propose an extension to two-phase locking, called altruistic locking, whereby LLTs can release their locks early. Transactions that access this released data are said to run in the wake of the LLT and must follow special locking rules. Like two-phase locking, altruistic locking is easy to implement and guarantees serializability.