bluuebunny/crossref_metadata_2025 huggingface dataset:
Weitzman's Approach and Conservation of Breed Diversity: an Application to African Cattle Breeds
Authors: Reist‐Marti S. B. , Simianer H. , Gibson J. , Hanotte O. , Rege J. E. O.
Published: September 2003

Abstract: To evaluate the Weitzman approach for assessing alternative conservation strategies for breed ( population ) diversity, we used genetic distance measures between 49 African cattle breeds divided into two groups of 26 taurine ( Bos taurus ) and sanga ( Bos taurus×Bos indicus ) breeds and 23 zebu ( Bos indicus ) and zenga ( sanga ×Bos indicus ) breeds. The derived maximum‐likelihood trees clearly displayed the geographic distribution and the zebu‐taurine admixture of the breeds. We developed a novel scheme to estimate the extinction probability for each breed which considered total population size, change of population size over the last 10 years, distribution of the breed, risk of indiscriminate crossing, organization among farmers, establishment of conservation schemes, political situation of the countries, special traits, sociocultural importance, and reliability of information. This scheme yielded reasonable estimates of extinction probabilities for the analyzed breeds, which were significantly influenced by the population size and its recent change, distribution of the breed, organization among farmers, establishment of conservation schemes, and reliability of information. The average extinction probability over all breeds and for each breed group was around 48%. Diversity in the zebu‐zenga group was only half the diversity in the taurine‐sanga group, mainly because of the lower number of breeds and their genetic origin. For both groups, the expected diversity after 20–50 years was about half the current diversity, and the coefficient of variation was about 20%. Our results suggest that the optimum conservation strategy is to give priority to those breeds with the highest marginal diversity, rather than to the most endangered breeds; thus, Madagascar Zebu and Muturu should be given conservation priority in their respective groups. Our study demonstrates that efficient conservation of genetic diversity with limited funds has to take genetic and nongenetic factors into account. Nongenetic factors are accounted for within our scheme to derive extinction probabilities. Within‐breed and within‐population diversity are not accounted for. Extending Weitzman's basic approach accordingly could yield an effective methodology for determining conservation strategies under highly varying circumstances and for many species, including wild organisms.
Ecological Effectiveness: Conservation Goals for Interactive Species
Authors: Soulé Michael E. , Estes James A. , Berger Joel , Del Rio Carlos Martinez
Published: September 2003

Abstract: The rarity or absence of highly interactive species leaves a functional void that can trigger linked changes leading to degraded or simplified ecosystems. A preliminary analysis indicates a relatively high frequency of such interactive species among endangered mammals. Rapid environmental change is likely to increase the interactivity of some species and reduce that of others over relatively short intervals. The current implementation of environmental policies and laws, such as the U.S. Endangered Species Act, generally ignores interspecific effects; recovery goals are autecological, short term, and numerically and spatially minimalistic. Moreover, by failing to account for interspecific interactions, recovery objectives are becoming indefensible in light of increasing knowledge from community ecology. Using the sea otter (   Enhydra lutris ) and wolf ( Canis lupus ) as examples, we argue that conservation plans should call for recovery or repatriation of such interactive species at ecologically effective densities in as many places as are currently realistic. It will be prudent and beneficial to estimate ecologically effective densities where there is disagreement among experts and interested parties about the desirability of restoring an interactive species to a particular region and to a particular density.
Effects of Experimental Forest Management on Density and Nesting Success of Bird Species in Missouri Ozark Forests
Authors: Gram Wendy K. , Porneluzi Paul A. , Clawson Richard L. , Faaborg John , Richter Stephen C.
Published: September 2003

Abstract:A critical step in understanding the relationship between forest management and bird populations is conducting studies that employ rigorous experimental designs, relate forest management to avian demography, and explore relationships at expanded temporal and spatial scales. The Missouri Ozark Forest Ecosystem Project ( MOFEP ) is a long‐term, large‐scale manipulative experiment that is testing the effects of even‐aged ( i.e., clearcutting ) and uneven‐aged ( i.e., selection cutting ) forest management on a suite of response variables in Missouri oak‐hickory forests. We report on the short‐term effects of these management systems on the density and reproductive success of birds by evaluating 5 years of preharvest and 3 years of postharvest data from MOFEP. Densities of mature forest species declined 24–69% on the control ( i.e., no timber harvest ) sites during post‐treatment years, confounding interpretation of treatment effects. Densities of both Kentucky Warblers ( Oporornis formosus ) and Worm‐eating Warblers ( Helmitheros vermivorus ) increased in treatment sites relative to control sites. Conversely, even‐aged management negatively affected Ovenbird ( Seiurus aurocapillus ) density. Treatment significantly and positively affected density of four of the six early successional species. Densities of Indigo Bunting (  Passerina cyanea ) and Yellow‐breasted Chat (  Icteria virens ) were significantly higher in both even‐aged and uneven‐aged treatments, whereas densities of Prairie Warbler (  Dendroica discolor ) and White‐eyed Vireo (  Vireo griseus ) were significantly higher in even‐aged treatments than in the controls. Nest success rates averaged 29% for all species and did not change significantly from pre‐ to post‐treatment years. Mature forest bird populations declined as trees were removed, but significant changes in nest predation and brood parasitism did not occur. In addition, openings associated with timber removal provided habitats for early successional species. We suggest that a mixed strategy of timber management may be necessary to support the full range of breeding birds in this region.
Inferring Vulnerability to Introduced Predators without Experimental Demonstration: Case Study of Suter's Skink in New Zealand
Authors: Towns David R. , Parrish G. Richard , Westbrooke Ian
Published: September 2003

Abstract: The coast‐inhabiting Suter's skink ( Oligosoma suteri ) has a fragmented distribution on islands around northern New Zealand, which has been attributed to the effects of introduced predators. We used classification trees to assess a range of factors that might influence the distribution of Suter's skinks. We then assessed the vulnerability to predation of juvenile and adult Suter's skinks by using a population viability analysis ( PVA ) model. We tested predictions from the classification tree and PVA models on two islands from which introduced Pacific rats (  Rattus exulans ) were removed. On one island, Suter's skinks were reintroduced ( assuming previous extirpation by rats ), and on the other the skinks had survived in the presence of Pacific rats. Our results revealed that populations of Suter's skinks are likely to be susceptible to predation where there are no bouldery beaches as refuges. Where these beaches are present, they are likely to function as refuges only if there is effective protection for adults. We conclude, however, that despite some apparently compelling circumstantial evidence of the effects of introduced predators on New Zealand lizards, it appears impractical to verify cause and effect with field manipulations if lizards and introduced predators do not already coexist.
Inclusion of Native and Alien Species in Temperate Nature Reserves: an Historical Study from Central Europe
Authors: Pyšek Petr , Jarošík Vojtěch , Kučera Tomáš
Published: September 2003

Abstract: We studied the establishment and inclusion of native and alien plant species in nature reserves in the Czech Republic. Our aim was to answer the following questions: Do young and old nature reserves contain the same proportion of invasive plant species? Does the time of their introduction affect their representation in these reserves? We obtained recent lists of vascular plant species for 302 reserves established since 1838 and designated the species as native or alien. We divided the latter category into archaeophytes and neophytes, introduced before and after 1500, respectively. The increase in the number of reserves and species was evaluated by inclusion curves. For inclusion curves describing an increase in the number of reserves, the estimated time of 50% inclusion indicated when half the reserves of a particular type were established. For inclusion curves describing an increase in the number of species, the estimated time of 50% inclusion indicated when half the species of a particular category ( native species, all aliens, archaeophytes, neophytes ), reported from the country, were included in the nature reserves. The forest and dry‐grassland reserves were established earlier than those in wetlands and peat bogs, whereas humid‐grassland reserves tended to be the most recently established. Half the native species were included significantly earlier ( after 25 years ) than half of alien species ( 86 years ), and half the neophytes were included later ( 143 years ) than half the archaeophytes ( 31 years ). Early reserves harbor a significantly lower number of alien species than those established later. These reserves include a higher proportion of the Czech Republic's native species and archaeophytes than of its neophytes. There was no difference in the relative rates of inclusion of native species, archaeophytes, and neophytes. However, the fact that the same inclusion rate applies to neophytes, a group with an increasing species pool, as to archaeophytes and native species, which both have constant species pools, suggests that natural vegetation in nature reserves is an effective barrier against the establishment of alien species. On a historical time scale, the early establishment of nature reserves in a given country decreases the probability that the reserve will be invaded by alien plants.
Long‐Term Range Recession and the Persistence of Caribou in the Taiga
Authors: Schaefer James A.
Published: September 2003

Abstract: Spatial patterns can help in understanding the decline and future prospects of threatened species, but the dynamics of range retraction have not been applied to these fundamental questions. I analyzed long‐term changes in occupancy by taiga‐dwelling caribou ( Rangifer tarandus caribou ) to estimate their rate of disappearance and time to extirpation in Ontario, Canada. Patterns of range recession, 1880–1990, indicated that half of historic woodland caribou range has been lost, a rate of disappearance of 34,800 km2 per decade, and a northward range recession of 34 km per decade. The mean metapopulation density, the abundance of discrete winter groups, was one group per 1,900 km2, suggesting an average loss of 18 caribou wintering areas per decade during this period. There was a strong coincidence between the recent southern limits of caribou occupancy and the northern front of forest harvesting, implying an anthropogenic agent of decline. The estimated time to extirpation of forest‐dwelling caribou in Ontario, inferred from the sustained rate of disappearance, was 91 years ( 95% confidence interval: 57–149 years ). The persistence of woodland caribou may depend on spatial separation from human incursion.
Natural Disturbances and Mining of Panamanian Coral Reefs by Indigenous People
Authors: Guzmán Héctor M. , Guevara Carlos , Castillo Arcadio
Published: September 2003

Abstract: Before the 1980s, coral reefs were considered relatively stable and healthy in Kuna‐Yala, Caribbean Panama. During the 1980s, however, several natural disturbances changed the reef's community structure. We evaluated historical changes in coral cover and for the first time provide quantitative evidence of a large‐scale process of reef degradation. This process started long before the onset of these disturbances as a result of demographic growth and the traditional practices of the Kuna people. Living coral cover declined 79% in 30 years ( 1970–2001 ) while the indigenous population increased 62%. We measured 20 km of seawall built with mined reef corals ( 16,000 m 3 ) and an increase in island surface area of 6.23 ha caused by coral land filling. Consequently, coastal erosion has increased as a result of the lack of a protective natural barrier and a 2.0 cm/year local increase in sea level. Coral‐mining and land‐filling practices to accommodate population expansion and mismanagement of resources have significantly modified the reef ecosystem and will have serious long‐term consequences. We propose eight priority conservation areas within the Indian reserve, based on reef conservation status. The Kuna people and their leaders are considering a cultural change, which may include a gradual and organized migration to the mainland, and have optimistically accepted our results.
A Checklist for Wildlands Network Designs
Authors: Noss Reed F.
Published: September 2003

Abstract: Systematic conservation planning requires rigorous methods. Methodological rigor and scientific defensibility are enhanced by conceptual frameworks, standards, and criteria for guiding and evaluating individual plans. The Wildlands Project is developing wildlands network designs in various regions across North America, based on the goals of rewilding—restoration of wilderness qualities and intact food webs—and biodiversity conservation. The project employs such modern conservation planning tools as spatially explicit habitat and population models and site‐selection algorithms. I created a checklist to assist staff, contractors, and cooperators with the Wildlands Project in the development of regional conservation assessments and wildlands network designs that are consistent with currently accepted standards for science‐based conservation planning. The checklist also has proven useful in the peer review of plans. The checklist consists of eight general standards, each of which includes several specific criteria that relate to the qualifications of staff, choice of biodiversity surrogates and goals, methodological comprehensiveness and rigor, replicability, analytic rigor, peer review, and overall quality of scholarship. Application of the checklist is meant to be flexible and to encourage creativity and innovation. Nevertheless, every plan must be scientifically defensible and must make the best use of available data, staff, and resources. Moreover, some degree of consistency is required to link individual plans together into a continental‐scale network. The checklist may provide a template that other conservation organizations, agencies, scientists, and activists can adapt to their programs.
Evaluation of serologic screening of blood donors in India reveals a lack of correlation between anti‐HBc titer and PCR‐amplified HBV DNA
Authors: Chaudhuri Vaishali , Nanu Ambika , Panda Subrat Kumar , Chand Prem
Published: September 2003

BACKGROUND:  Transfusion associated‐HBV (TAHBV) is estimated at approximately 1.5 percent in postsurgical recipients and 50 percent or more in multiple‐transfusion recipients in India. Not transfusing blood with high‐titer anti‐HBc, which reportedly correlates with the presence of HBV DNA, helped reduce TAHBV in Japan. This study tested anti‐HBc‐reactive donors for PCR‐amplified HBV DNA and its correlation with anti‐HBc titers.

STUDY DESIGN AND METHODS:  In total, 30,853 donors from Cohort 1 (24,694 in 2001) and Cohort 2 (6159 in 2000) were screened for anti‐HBc and anti‐HBs. Amplification of HBV DNA was performed on an unselected subset of 147 out of 3304 anti‐HBc‐only sera from Cohort 1 and 230 out of 6159 from Cohort 2. Correlation of anti‐HBc titers in DNA positive (n = 48), DNA negative (n = 40), anti‐HBs reactive (n = 44), and HBsAg reactive (n = 45) donors was by Fisher's exact test.

RESULTS:  In Cohort 1, 2673 (10.82%) donors were reactive for anti‐HBc, of whom 1038 (4.20%) were anti‐HBc only. HBV DNA was detected in 40 out of 147 (27.21%) and 48 out of 230 (20.87%) donors with anti‐HBc only from the two cohorts. Anti‐HBc titers detected no significant difference between the first three groups.

CONCLUSION:  Cryptic HBV infection was observed in approximately 25 percent of anti‐HBc‐only donors. No correlation was established between HBc titers and presence of HBV DNA.
Randomized placebo‐controlled study of oral calcium carbonate administration in plateletpheresis: I. Associations with donor symptoms
Authors: Bolan Charles D. , Wesley Robert A. , Yau Yu Ying , Cecco Stacey A. , Starling Judith , Oblitas Jaime M. , Rehak Nadja N. , Leitman Susan F.
Published: September 2003

BACKGROUND:  The effect of oral calcium (Ca) supplements in preventing citrate‐induced symptoms during plateletpheresis was evaluated in a randomized, blinded, placebo‐controlled trial.

STUDY DESIGN AND METHODS:  Twenty‐three donors (12 men, 11 women) underwent four plateletpheresis procedures each, ingesting either 1 or 2 g of oral Ca carbonate or an equivalent placebo 30 minutes before donation. Ten of these subjects subsequently ingested 4 g of open‐label Ca before a fifth procedure. All procedures were conducted at the same citrate infusion rate (1.5 mg/kg/min) for 90 minutes.

RESULTS:  Ingestion of 2 g of oral Ca resulted in a significant reduction in the severity of paresthesias and a significant, though modest, increase in serum ionized calcium (iCa), but no significant improvement in total symptom scores, compared to placebo. Minimal effects were seen with the 1‐g dose. The two factors most highly correlated with development of severe symptoms were decreased levels of iCa and ionized magnesium (iMg) at 30 minutes into apheresis. Lower preapheresis serum albumin, creatinine, vitamin D, iMg, and total Mg concentrations were also significantly associated with symptoms. Women experienced more frequent and severe symptoms than men, however, gender was not associated with symptoms after adjustment for lower serum albumin, creatinine, and Mg levels. Ingestion of 4 g of Ca offered no improvement in symptoms or iCa levels compared with the 2‐g dose.

CONCLUSION:  Prophylactic oral Ca was associated with modest improvements in citrate‐induced symptoms and laboratory parameters. Baseline albumin and Mg levels were strongly predictive of the development of symptoms. In donors with a prior history of uncomfortable citrate‐related effects, a 2‐g oral Ca dose before apheresis is recommended.
Acute intravascular hemolysis after transfusion of a chimeric RBC unit
Authors: Pruss Axel , Heymann Guido A. , Hell Anette , Kalus Ulrich J. , Krausch Dietmar , Dörner Thomas , Kiesewetter Holger H. , Salama Abdulgabar
Published: September 2003

BACKGROUND:  Natural blood cell chimerism rarely occurs in humans. The case of a patient who developed transfusion reaction due to the transfusion of chimeric RBCs is reported.

CASE REPORT:  A 61‐year‐old male patient with blood group O received two units of packed and O‐grouped RBCs after elective kidney surgery. Immediately after blood transfusion, the patient developed a hemolytic transfusion attack. The serologic re‐examination revealed only a mixed‐field pattern of agglutination of RBCs in one of the two transfused units. The donor of this unit was an apparently healthy 24‐year‐old male with a twin sister. Both of them showed an identical mixture of roughly 95 percent group O and 5 percent group B RBCs by gel agglutination technology and flow cytometry. The results were also confirmed by ABO blood group genotyping.

CONCLUSIONS:  This is the first report of a hemolytic transfusion reaction related to the transfusion of chimeric RBCs.
Absence of activation of CMV by blood transfusion to HIV‐infected, CMV‐seropositive patients
Authors: Drew W. Lawrence , Chou Sunwen , Mohr Beth A. , Assmann Susan F. , Miner Richard C. , Laycock Megan E. , Busch Michael P. ,   Viral Activation Transfusion Study Group
Published: September 2003

BACKGROUND:  The Viral Activation Transfusion Study (VATS) afforded an opportunity to determine whether blood transfusions, and in particular exogenous WBCs, “activate” CMV replication in HIV‐infected, CMV‐seropositive patients, and whether such patients can be superinfected by additional strains of CMV transmitted via blood transfusions.

STUDY DESIGN AND METHODS:  A total of 531 patients were randomized to receive either WBC‐reduced (WBCR) or non‐WBC‐reduced (NWBCR) RBC units. Plasma CMV PCR assays were performed before transfusion and weekly after transfusion for 4 weeks. NWBCR cases with evidence of possible reactivation and/or superinfection were further studied for donor viremia by DNA PCR of frozen retention segments and new genotype acquisition using gB envelope sequence analysis of pre‐ and posttransfusion recipient specimens.

RESULTS:  VATS patients received a median of two RBC units during their initial transfusion. Whether positive or negative for CMV DNA at baseline, there were no significant treatment‐arm differences in the percentage of patients who had positive qualitative CMV PCR or increases in CMV viral load at follow‐up. Of 50 recipients randomized to NWBCR RBC and meeting criteria for possible CMV superinfection, 25 had sufficient CMV DNA load in a baseline and one or more viremic follow‐up sample to permit comparison of gB genotypes. Only two recipients showed genotype shifts. Of 125 WBC pellets prepared from the seropositive units transfused into these 50 cases, only 1 tested weakly PCR positive for CMV DNA (insufficient copy number for genotyping).

CONCLUSION:  There was no evidence of “activation” of CMV by blood transfusion. Among the NWBCR RBC recipients, there was little evidence of possible transmission of new CMV strains. Hence, the current policy for transfusion support of HIV‐infected patients, which allows transfusion of CMV‐antibody‐positive blood to CMV‐seropositive patients, is appropriate.
Comparison of radioisotope methods and a nonradioisotope method to measure the RBC volume and RBC survival in the baboon
Authors: Valeri C. Robert , MacGregor Hollace , Giorgio Albert , Srey Rithy , Ragno Gina
Published: September 2003

BACKGROUND:  RBC volume, 24‐hour posttransfusion survival, and life span can be measured with radio‐isotopes and nonradioactive procedures.

STUDY DESIGN AND METHODS:  RBC volume was measured directly with autologous baboon RBCs labeled with biotin‐X‐N‐hydroxysuccinimide (NHS), 51Cr, 99mTc, and 111In‐oxine and indirectly from the 125I plasma volume and the total body Hct. Twenty‐four‐hour posttransfusion survival and life span were measured in autologous fresh baboon RBCs labeled with 51Cr, 111In‐oxine, 99mTc, and biotin‐X‐NHS.

RESULTS:  Significantly larger RBC volumes were observed when the fresh autologous RBCs were labeled with 51Cr, 111In‐oxine, or 99mTc than when they were labeled with the nonradioactive biotin‐X‐NHS. Twenty‐four‐hour posttransfusion survival values were signifi‐cantly lower in the RBCs labeled with 111In‐oxine or 99mTc than in the RBCs labeled with 51Cr.

CONCLUSIONS:  The greater in vivo elution of 51Cr, 111In‐oxine, and 99mTc than that of biotin‐X‐NHS influenced the measurements of RBC volume, 24‐hour posttransfusion survival, and life span of the fresh baboon RBCs.
Severe neonatal alloimmune thrombocytopenia caused by antibodies to human platelet antigen 3a (Baka) detectable only in whole platelet assays
Authors: Harrison C.R. , Curtis B.R. , McFarland J.G. , Huff R.W. , Aster R.H.
Published: September 2003

BACKGROUND:  Maternal antibodies that cause neonatal alloimmune thrombocytopenia are commonly identified by solid‐phase assays that detect the causative antibodies on the basis of their reactions with specific PLT glycoproteins. Two cases of severe neonatal alloimmune thrombocytopenia caused by maternal antibodies specific for human PLT antigen 3a (HPA‐3a [Baka]) that failed to give the expected reactions in some solid‐phase assays were recently encountered.

STUDY DESIGN AND METHODS:  PLT‐reactive antibodies were characterized by three different solid‐phase assays and by flow cytometry.

RESULTS:  The two maternal antibodies gave negative reactions in the antigen capture ELISA, modified antigen capture ELISA, and MoAb immobilization of PLT antigens tests but reacted strongly in flow cytometry with intact PLTs that were HPA‐3a+. Other sera samples specific for HPA‐3a reacted equally well in all assays.

CONCLUSIONS:  The two antibodies appear to recognize an epitope on the HPA‐3a+ form of glycoprotein IIb that is lost when PLTs are solubilized in detergent, as required for solid‐phase assays. The diagnosis was made in these cases because no HLA antibodies were present, allowing an HPA‐3a‐specific reaction to be identified with intact PLTs as targets. Such antibodies are likely to be overlooked when HLA antibodies are also present.
HIV antibody screening remains indispensable for ensuring viral safety of blood components despite NAT implementation
Authors: Laperche Syria , Morel Pascal , Deschaseaux Marie , Bouchardeau Françoise , Alimardani Gulie , Guillaume Nicolas , Rouger Philippe , Lefrère Jean‐Jacques
Published: September 2003

BACKGROUND:  The main objective of the imple‐mentation of NAT for the screening of blood‐borne viruses was to compensate for the failure of serologic assays during the window period. Because this new screening procedure theoretically covers the entire period of infectivity, the necessity for maintaining serologic assays in blood screening strategy could become questionable.

STUDY DESIGN AND METHODS:  To investigate this issue, a panel of 35 samples has been studied by NAT. These samples had been collected from HIV‐1 antibody‐positive individuals presenting a persistently low viral RNA load (<400 copies/mL) in the absence of antiviral therapy. All samples were analyzed with the minipool (×8) NAT routinely used in blood bank setting (HIV‐1 and HCV assay based on transcription‐mediated amplification) and with single‐donation testing.

RESULTS:  The minipool NAT failed to detect the presence of HIV RNA in 15 of the 35 samples (11 remained negative when retested). Single‐donation testing gave negative results in 4 samples (3 remained negative when retested). Fourteen of the 18 samples with a viral load greater than 50 copies per mL were positive by minipool NAT versus 6 of the 17 samples with fewer than 50 copies per mL (p = 0.02).

CONCLUSION:  The results clearly demonstrate that anti‐HIV screening should not be withdrawn from biologic qualification procedures of blood donations, even when single NAT is performed.
Magnetic domain wall motion triggered by an electric current
Authors: Tsoi M. , Fontana R. E. , Parkin S. S. P.
Published: September 2003

The current-induced propagation of magnetic domain walls is studied in CoFe nanoconstrictions patterned by electron beam lithography. Propagation of the walls was confirmed by magnetic force microscopy imaging. The device geometry allows us to distinguish between various mechanisms of interaction between electric current and domain walls: a mechanism in which spin transfer associated with current traversing a domain wall dominates. As expected for such a mechanism the domain wall propagation occurs in the direction of electron current flow and has a current threshold of the order ∼1011 A/m2.
Positive operator valued measures covariant with respect to an irreducible representation
Authors: Cassinelli G. , De Vito E. , Toigo A.
Published: September 2003

Given an irreducible representation of a group G, we show that all the covariant positive operator valued measures based on G/Z, where Z is a central subgroup, are described by trace class, trace one positive operators.
n=3
differential calculus and gauge theory on a reduced quantum plane
Authors: El Baz M. , El Hassouni A. , Hassouni Y. , Zakkari E. H.
Published: September 2003

We discuss the algebra of N×N matrices as a reduced quantum plane. A n=3-nilpotent deformed differential calculus involving a complex parameter q is constructed. The two cases, q 3rd and Nth root of unity are completely treated. As an application, we establish a gauge field theory for the particular cases n=2 and n=3.
Development and testing of a frequency-agile optical parametric oscillator system for differential absorption lidar
Authors: Weibring P. , Smith J. N. , Edner H. , Svanberg S.
Published: September 2003

An all-solid-state fast-tuning lidar transmitter for range- and temporally resolved atmospheric gas concentration measurements has been developed and thoroughly tested. The instrument is based on a commercial optical parametric oscillator (OPO) laser system, which has been redesigned with piezoelectric transducers mounted on the wavelength-tuning mirror and on the crystal angle tuning element in the OPO. Piezoelectric transducers similarly control a frequency-mixing stage and doubling stage, which have been incorporated to extend system capabilities to the mid-IR and UV regions. The construction allows the system to be tuned to any wavelength, in any order, in the range of the piezoelectric transducers on a shot-to-shot basis. This extends the measurement capabilities far beyond the two-wavelength differential absorption lidar method and enables simultaneous measurements of several gases. The system performance in terms of wavelength, linewidth, and power stability is monitored in real time by an étalon-based wave meter and gas cells. The tests showed that the system was able to produce radiation in the 220–4300-nm-wavelength region, with an average linewidth better than 0.2 cm−1 and a shot-to-shot tunability up to 160 cm−1 within 20 ms. The utility of real-time linewidth and wavelength measurements is demonstrated by the ability to identify occasional poor quality laser shots and disregard these measurements. Also, absorption cell measurements of methane and mercury demonstrate the performance in obtaining stable wavelength and linewidth during rapid scans in the mid-IR and UV regions.
Variable-ambient scanning stage for a laser scanning confocal microscope
Authors: Sirbuly D. J. , Schmidt J. P. , Mason M. D. , Summers M. A. , Buratto S. K.
Published: September 2003

A variable-ambient scanning stage for a laser scanning confocal microscope was designed and tested. The stage allows for facile observation of both thin films and single molecule samples under inert conditions. High precision images have been acquired up to 174 μm2 using a single piezoceramic tube. The vacuum seal is achieved by simply placing the sample side of a standard 25×25 mm glass coverslip face down onto a Buna o ring and gently clamping it in place with a Teflon cap. Tests show that the stage holds a vacuum of at least 3×10−6 Torr. Fluorescence experiments performed on films of an organic dye, DiIC12, as well as single molecule experiments performed on air sensitive oligo(phenylenevinylene) molecules, effectively demonstrate the ability of the scanner to reduce photo-oxidation rates.
Long-Alfvén-wave trains in collisionless plasmas. I. Kinetic theory
Authors: Passot T. , Sulem P. L.
Published: September 2003

A generalized kinetic derivative nonlinear Schrödinger equation for the multidimensional dynamics of Alfvén wave trains propagating along an ambient magnetic field is derived from the Vlasov–Maxwell equations by a reductive perturbative expansion. It retains in addition to the Landau damping, the coupling to longitudinally averaged fields driven by both transverse gradients and kinetic effects. These mean fields that modulate the propagation speed of the wave play a main role in transverse instabilities of extended Alfvén wave packets and in the filamentation phenomenon. This long-wave model also provides a benchmark for Landau-fluid descriptions of collisionless plasmas.
Long-Alfvén-wave trains in collisionless plasmas. II. A Landau-fluid approach
Authors: Passot T. , Sulem P. L.
Published: September 2003

A Hall Landau-fluid model where the fluid hierarchy is closed by nonlocal dynamical equations for the heat fluxes is constructed, based on a weakly nonlinear description of long parallel Alfvén waves in a collisionless plasma. This model which is shown to accurately reproduce the above asymptotic regime, can be viewed as a first step towards the simulation of dispersive Alfvén wave turbulence with a realistic dissipation.
Pauli approximations to the self-adjoint extensions of the Aharonov–Bohm Hamiltonian
Authors: Borg J. L. , Pulé J. V.
Published: September 2003

It is well known that the formal Aharonov–Bohm Hamiltonian operator, describing the interaction of a charged particle with a magnetic vortex, has a four-parameter family of self-adjoint extensions, which reduces to a two-parameter family if one requires that the Hamiltonian commutes with the angular momentum operator. The question we study here is which of these self-adjoint extensions can considered as limits of regularized Aharonov–Bohm Hamiltonians, that is Pauli Hamiltonians in which the magnetic field corresponds to a flux tube of nonzero diameter. We show that not all the self-adjoint extensions in this two-parameter family can be obtained by these approximations, but only two one-parameter subfamilies. In these two cases we can choose the gyromagnetic ratio in the approximating Pauli Hamiltonian in such a way that we get convergence in the norm resolvent sense to the corresponding self-adjoint extension.
Stratified reduction of many-body kinetic energy operators
Authors: Iwai Toshihiro , Yamaoka Hidetaka
Published: September 2003

The center-of-mass system of many bodies admits a natural action of the rotation group SO(3). According to the orbit types for the SO(3) action, the center-of-mass system is stratified into three types of strata. The principal stratum consists of nonsingular configurations for which the isotropy subgroup is trivial, and the other two types of strata consist of singular configurations for which the isotropy subgroup is isomorphic with either SO(2) or SO(3). Depending on whether the isotropy subgroup is isomorphic with SO(2) or SO(3), the stratum in question consists of collinear configurations or of a single configuration of the multiple collision. It is shown that the kinetic energy operator is expressed as the sum of rotational and vibrational energy operators on each stratum except for the stratum of multiple collision. The energy operator for nonsingular configurations has singularity at singular configurations. However, the singularity is not essential in the sense that both of the rotational and vibrational energy integrals have a finite value. This can be proved by using the boundary conditions of wave functions at singular configurations for three-body systems, for simplicity. It is shown, in addition, that the energy operator for collinear configurations has also singularity at the multiple collision, but the singularity is not essential either in the sense that the kinetic energy integral is not divergent at the multiple collision. Reduction procedure is applied to the respective energy operators for the nonsingular and the collinear configurations to obtain respective reduced operators, both of which are expressed in terms of internal coordinates.
Covariant realization of quantum spaces as star products by Drinfeld twists
Authors: Blohmann Christian
Published: September 2003

Covariance of a quantum space with respect to a quantum enveloping algebra ties the deformation of the multiplication of the space algebra to the deformation of the coproduct of the enveloping algebra. Since the deformation of the coproduct is governed by a Drinfeld twist, the same twist naturally defines a covariant star product on the commutative space. However, this product is in general not associative and does not yield the quantum space. It is shown that there are certain Drinfeld twists which realize the associative product of the quantum plane, quantum Euclidean four-space, and quantum Minkowski space. These twists are unique up to a central two-coboundary. The appropriate formal deformation of real structures of the quantum spaces is also expressed by these twists.
A quantum weak energy inequality for spin-one fields in curved space–time
Authors: Fewster Christopher J. , Pfenning Michael J.
Published: September 2003

Quantum weak energy inequalities (QWEI) provide state-independent lower bounds on averages of the renormalized energy density of a quantum field. We derive QWEIs for the electromagnetic and massive spin-one fields in globally hyperbolic space–times whose Cauchy surfaces are compact and have trivial first homology group. These inequalities provide lower bounds on weighted averages of the renormalized energy density as “measured” along an arbitrary timelike trajectory, and are valid for arbitrary Hadamard states of the spin-one fields. The QWEI bound takes a particularly simple form for averaging along static trajectories in ultrastatic space–times; as specific examples we consider Minkowski space (in which case the topological restrictions may be dispensed with) and the static Einstein universe. A significant part of the paper is devoted to the definition and properties of Hadamard states of spin-one fields in curved space–times, particularly with regard to their microlocal behavior.
Transition from unbounded to bounded whistler wave dispersion: Reconsidered
Authors: Franck Christian M. , Kleiber Ralf , Bonhomme Gérard , Grulke Olaf , Klinger Thomas
Published: September 2003

The whistler wave dispersion relation in the transition region between unbounded and bounded plasma geometry is investigated experimentally and numerically. Measurements are done in a linear magnetized helicon plasma covering the large frequency range from 100–800 MHz, corresponding to 0.06–0.5fce. Small wavelength wave propagation (λ≪d: plasma diameter) is well explained by unbounded plasma whistler wave dispersion. In contrast to previously reported measurements [Franck et al., Phys. Plasmas 9, 3254 (2002)], the experimental findings are compared to numerical results obtained from the differential equations of a plasma-filled waveguide. Long wavelength wave measurements show that there is only qualitative agreement even with dispersion theory of whistler wave propagation in bounded plasmas. This is attributed to the perpendicular wave mode structure that influences the parallel wavelengths. Measurements of the perpendicular wave mode structure shows that it is basically given by the diameter of the plasma column diameter rather than the conducting vessel with a dependence on the wave frequencies; two findings which are neglected so far in simple theory. These results are fully consistent with the numerical solutions.
Hardware simulator for photon correlation spectroscopy
Authors: Ferri Fabio , Magatti Davide
Published: September 2003

We present a hardware simulator ideal for testing digital correlators in photon correlation spectroscopy. By using a PCI-6534 National Instrument I/O board, a personal computer (1.5 GHz Pentium 4), and an original algorithm developed in LabVIEW (National Instrument™), we realized an instrument capable of delivering a continuous stream of transistor-transistor logic pulses with the desired statistical properties over one or more channels. The pulse resolution could be set to values multiple of the clock period Δt=50 ns available on the board. When a single channel is used, the maximum count rate at Δt=50 ns was 〈I〉∼350 kHz. With two channels we obtained 〈I〉∼80 kHz at Δt=50 ns and 〈I〉∼120 kHz at Δt=100 ns. Pulse streams with Gaussian statistics and in the presence of shot noise were simulated and measured with a commercial hardware correlator. Photodetector defects, such as the presence of afterpulses, were also simulated and their elimination by cross correlation techniques was checked. The simulator works also as a general purpose pulse pattern generator (PPG). Compared with commercial PPGs, our simulator is slower, but permits a continuous output of the pulse stream (not allowed in PPGs). At the same time it offers many other nontrivial advantages related to its flexibility, relatively low cost, and easy adaptability to future technology developments.
Interferometric setup for measurements of expansion of whisker-like samples
Authors: Golovnya A. V. , Pokrovskii V. Ya.
Published: September 2003

We describe a simple technique for study of (thermal) expansion of whisker-like samples. At the heart of the method is the measurement of the shift of the sample middle, which is lifted over the substrate, while the ends of the sample are fixed at the substrate. The optical interference technique allows one to detect the relative length change about 5×10−7. Simultaneous electric measurements of the sample can be performed. We illustrate the technique with the study of TaS3, a quasi-one-dimensional conductor with charge-density waves: thermal expansivity has been measured and hysteresis in thermal expansion is found.
String effects on elastic collisions of ions with strings of dust grains in dusty plasmas
Authors: Jung Young-Dae
Published: September 2003

The elastic collision of ions with strings of strongly coupled dust grains in dusty plasmas is investigated using the eikonal analysis. The dust string has been considered as the one-dimensional model for strongly coupled dusty plasmas. The impact parameter method is applied to investigate the variation of the eikonal phase and elastic cross section as functions of the Debye length, number of dust grains, spacing of dust grains, and collision energy. The result shows that the eikonal phase and the total scattering cross section are increased with increasing Debye length. It is also found that the eikonal phase increases with increasing dust spacing, i.e., the length of dust string, and with the increasing number of dust grains due to the collective effects.
Relativistic heat conduction and thermoelectric properties of nonuniform plasmas
Authors: Honda M.
Published: September 2003

Relativistic heat transport in electron-two-temperature plasmas with density gradients has been investigated. The Legendre expansion analysis of relativistically modified kinetic equations shows that strong inhibition of heat flux appears in relativistic temperature regimes, suppressing the classical Spitzer–Härm conduction. The Seebeck coefficient, the Wiedemann–Franz law, and the thermoelectric figure of merit are derived in the relativistic regimes.
Multipactor in low pressure gas
Authors: Udiljak R. , Anderson D. , Lisak M. , Semenov V. E. , Puech J.
Published: September 2003

The effect of electron-neutral collisions on the multipactor threshold in a low pressure gas is analyzed in the case when the ionization energy of the gas particles is larger than the impact energy of the oscillating electrons. It is found that a higher microwave power is required to initiate multipactor, since the collisions tend to slow down the electrons. It is also found that the phase limits, within which multipactor can occur, are affected by the presence of the low density gas. Transition to the regime of corona discharges is also discussed.
Isomonodromy deformations for the ZS-AKNS system with quadratic spectral variables
Authors: Wu Derchyi
Published: September 2003

We solve the monodromy problem and prove the Painleve property for self-similar ZS-AKNS flows with a quadratic spectral variable in this report. In particular, we obtain meromorphic solutions for the Cauchy problem of the self-similar derivative nonlinear Schrödinger equation.
A matrix model for the β-Jacobi ensemble
Authors: Lippert Ross A.
Published: September 2003

This note presents a random matrix model for general (β>0) β-Jacobi ensembles. This generalizes the well-known MANOVA models for β=1,2,4 and eliminates the quantization of β (and other parameters) present in the previously known models. This model is a partial answer to an open problem presented by Dumitriu and Edelman, where they also presented models for the β-Laguerre and β-Hermite ensembles.
Group theory approach to the Dirac equation with a Coulomb plus scalar potential in D+1 dimensions
Authors: Dong Shi-Hai , Sun Guo-Hua , Popov Dušan
Published: September 2003

We generalize the Dirac equation to D+1 space–time. The conserved angular momentum operators and their quantum numbers are discussed. The eigenfunctions of the total angular momentums are calculated for both odd D and even D cases. The exact solutions of the D+1-dimensional radial equations of the Dirac equation with a Coulomb plus scalar potential are analytically presented by studying the Tricomi equations obtained from a pair of coupled first-order ones. The eigenvalues are also discussed in some detail.
The indefinite anti-self-dual metrics and the Painlevé equations
Authors: Okumura Shoji
Published: September 2003

We classify the SU(2)-invariant anti-self-dual metrics with a signature (+, +, −, −). The metrics are specified by a solution of Painlevé VI, V, III or II. Moreover, we show the geometric meaning of the metrics specified by each type of Painlevé function.
Particle kinetic equation including weakly turbulent mode coupling
Authors: Yoon Peter H. , Ryu Chang-Mo , Rhee Tongnyeol
Published: September 2003

In this article, particle kinetic equations which incorporate the nonlinear wave–particle interaction, as derived in P. H. Yoon [Phys. Plasmas 7, 4858 (2000)] and V. N. Tsytovich [Theory of Turbulent Plasma (Consultants Bureau, New York, 1977), pp. 103–110] are re-examined. A unified formalism is obtained after discrepancies in both references are resolved. The present particle kinetic equation is valid for the velocity space which does not satisfy the linear wave–particle resonance condition, ω−k⋅v≠0, but when the particle velocity of interest primarily satisfies the nonlinear wave–particle resonance, ω−ω′−(k−k′)⋅v=0.
Effect of parallel velocity shear on the electrostatic ion-cyclotron instability in filamentary current channels
Authors: Agrimson Erick , Kim Su-Hyun , D’Angelo Nicola , Merlino Robert L.
Published: September 2003

The effect of magnetic field-aligned ion flow with a transverse flow velocity gradient (parallel velocity shear) on the excitation of the electrostatic ion cyclotron (EIC) instability in narrow current channels (width<ion gyroradius) is studied experimentally in a double-ended Q machine. The presence of parallel velocity shear may lead to the excitation of the EIC instability even in current filaments too small to otherwise support the instability.
Seiberg–Witten monopole equations on noncommutative R4
Authors: Popov Alexander D. , Sergeev Armen G. , Wolf Martin
Published: September 2003

It is well known that, due to vanishing theorems, there are no nontrivial finite action solutions to the Abelian Seiberg–Witten (SW) monopole equations on Euclidean four-dimensional space R4. We show that this is no longer true for the noncommutative version of these equations, i.e., on a noncommutative deformation Rθ4 of R4 there exist smooth solutions to the SW equations having nonzero topological charge. We introduce action functionals for the noncommutative SW equations and construct explicit regular solutions. All our solutions have finite energy. We also suggest a possible interpretation of the obtained solutions as codimension four vortex-like solitons representing D(p−4)- and D(p−4)¯-branes in a Dp-Dp¯ brane system in type II superstring theory.
Semiclassical asymptotics for the Maxwell–Dirac system
Authors: Sparber C. , Markowich P.
Published: September 2003

We study the coupled system of Maxwell and Dirac equations from a semiclassical point of view. A rigorous nonlinear WKB-analysis, locally in time, for solutions of (critical) order O(ε) is performed, where the small semiclassical parameter ε≪1 denotes the microscopic/macroscopic scale ratio.