Researching Pacific island livelihoods: mobility, natural resource management and nissology   总被引：1，自引：1，他引：0  

Christensen AE  Mertz O 《Asia Pacific viewpoint》2010,51(3):278-287

Small island literature is vast in focus and aim, and is rooted in many different disciplines. The challenge is to find common grounds for researching small islands conceptually and theoretically. The aim of this article is to comment on how to research small islands, including a discussion on contemporary theories of nissology and conceptual analytical frameworks for island research. Through a review of selected case-study-based island literature on changing livelihoods coming out of the South Pacific, we wish to illustrate and discuss advantages of finding common grounds for small island studies. The focus is on two dimensions of island livelihood, migration and natural resource management, both of which are significant contributors in making island livelihoods and shaping Pacific seascapes. We argue that there is still a substantial lack of studies targeting small island dynamics that are empirical and interdisciplinary in focus and link socio-economic and ecological processes of small island societies at temporal and analytical scales.  相似文献   

Pathogenomics of Culex quinquefasciatus and meta-analysis of infection responses to diverse pathogens     

Bartholomay LC  Waterhouse RM  Mayhew GF  Campbell CL  Michel K  Zou Z  Ramirez JL  Das S  Alvarez K  Arensburger P  Bryant B  Chapman SB  Dong Y  Erickson SM  Karunaratne SH  Kokoza V  Kodira CD  Pignatelli P  Shin SW  Vanlandingham DL  Atkinson PW  Birren B  Christophides GK  Clem RJ  Hemingway J  Higgs S  Megy K  Ranson H  Zdobnov EM  Raikhel AS  Christensen BM  Dimopoulos G  Muskavitch MA 《Science (New York, N.Y.)》2010,330(6000):88-90

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Endospores,prokaryotes, and microbial indicators in arable soils from three long-term experiments     

Paulina Tamez-Hidalgo  Bent T. Christensen  Mark A. Lever  Lars Elsgaard  Bente Aa. Lomstein 《Biology and Fertility of Soils》2016,52(1):101-112

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Nitrogen conserving potential of successive ryegrass catch crops in continuous spring barley   总被引：3，自引：0，他引：3  

I.K. Thomsen  B.T. Christensen 《Soil Use and Management》1999,15(3):195-200

Abstract. The nitrogen (N) conserving effects of Italian ryegrass ( Lolium multiflorum L.) undersown as a nitrate catch crop in spring barley ( Hordeum vulgare L.) were evaluated over a ten-year period in outdoor lysimeters (1.5 m deep, diam. 1 m) with sandy loam soil. Spring barley grown every year received 11.0 or 16.5 g N m⁻² before planting or was kept unfertilized. The N was given either as calcium ammonium nitrate or as ammoniacal N in pig slurry. From 1985 to 1989, ryegrass was undersown in the barley in half of the lysimeters while barley was grown alone in the remaining lysimeters. The grass sward was left uncut after barley harvest and incorporated in late winter/early spring. From 1990 to 1994 all lysimeters were in barley only.
Barley dry matter yields and crop N offtakes were not affected by the presence of undersown ryegrass, although grain yields appeared to be slightly reduced. After termination of ryegrass growing, N offtake in barley (grain+straw) was higher in lysimeters in which catch crops had been grown previously.
The loss of nitrate by leaching increased with N addition rate. Regardless of N dressing, ryegrass catch crops halved the total nitrate loss during 1985–1989, corresponding to a mean annual reduction in nitrate leaching of 2.0–3.5 g N m⁻². From 1990 to 1994, lysimeters previously undersown with ryegrass lost more nitrate than lysimeters with no history of ryegrass. The extra loss of nitrate accounted for 30% of the N retained by ryegrass catch crops during 1985–1989.
It is concluded that a substantial proportion of the N saved from leaching by ryegrass catch crops is readily mineralized and available for crop offtake as well as leaching as nitrate. To maximize benefits from ryegrass catch crops, the cropping system must be adjusted to exploit the extra N mineralization derived from the turnover of N incorporated in ryegrass biomass.  相似文献   

A seroepidemiological survey of Leptospira bratislava infections in Danish sow herds     

J. Mousing  J. Christensen  J. Haugegaard  A. L. Schirmer  N. F. Friis 《Preventive veterinary medicine》1995,23(3-4):201-213

A total of 796 sows and gilts from 30 Danish sow herds were examined three times at intervals of 6 weeks for serum antibodies to Leptospira bratislava by the microscopic agglutination technique (MAT) test. The prevalence of seroreactors with positive titer values, 1:100, at the three successive tests were 2.7%, 2.5% and 2.9%; 4.5% of the animals were positive in at least one of the three tests, and 2.2% showed a greater than two-fold rise in titer between two consecutive samplings. Of the 30 herds, 21 (70%) had ever-positive within-herd prevalences in sows and gilts of 4–13%. The risk of a herd having one or more positive sow was positively associated with a herd size of > 141 sows, and distinct regional differences in the prevalence of positive herds were observed. The reproductive performance of the 21 herds with seroreactions was poorer than the performance of the nine herds without positive reactions concerning the variables: ‘days from weaning to last service’ (2.7 days more, P = 0.07), ‘percentage of sows returning to heat’ (4.0 percentage units more, P = 0.03), ‘services per farrowing’ (0.04 more, P = 0.04), ‘farrowing percentage’ (4.3 percentage units lower, P = 0.06), and ‘stillborn pigs per farrowing’ (0.16 more, P = 0.02). No association between the MAT serological status of the herd and the incidence of medical treatments of sows and gilts could be found. A high prevalence and low cumulative incidence of seroreactors was demonstrated in first-parity gilts, followed by a low prevalence and cumulative incidence from parity 2 to 3, and a high prevalence and cumulative incidence at the fifth parity.  相似文献   

Induced LH release in spayed cows   总被引：1，自引：0，他引：1  

R E Short  B E Howland  R D Randel  D S Christensen  R A Bellows 《Journal of animal science》1973,37(2):551-557

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New horizons for veterinary medicine. What is Probe '73 suggesting?          下载免费PDF全文

G C Christensen 《The Canadian veterinary journal. La revue veterinaire canadienne》1974,15(1):21-23

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Rectal palpation and transmission of bovine leukemia virus in dairy cattle.     

S G Hopkins  R F DiGiacomo  J F Evermann  J D Christensen  D P Deitelhoff  W D Mickelsen 《Journal of the American Veterinary Medical Association》1991,199(8):1035-1038

To determine whether rectal palpation, using common obstetrical sleeves, serves as a mode of transmission of bovine leukemia virus in dairy cattle, field studies were conducted at 2 dairies. At a commercial dairy, significant difference was not observed in rate of seroconversion in heifers and cows in which the same sleeve or new sleeves were used for palpations. At a university dairy, where cattle were used to teach dairy husbandry and veterinary procedures, significantly (P less than 0.02) greater rate of seroconversion was observed in heifers and cows palpated with unwashed common sleeves than that observed in heifers and cows palpated with sleeves washed between use. Although rectal transmission of bovine leukemia virus under field conditions was documented, it was related to frequency of palpation and age of cattle.  相似文献   

Development of immunity to Ostertagia ostertagi (Trichostrongylidae: Nematoda) in pastured young cattle.     

J. Grnvold  P. Nansen  L. C. Gasbarre  C. M. Christensen  M. Larsen  J. Monrad  N. Midtgaard 《Acta veterinaria Scandinavica》1992,33(4):305-316

This experiment comprised 3 groups of calves, (+P2), (-P2) and (-P1), which all started their first grazing season as parasite-free calves. The (+P2)- and (-P2)-group grazed 2 seasons. In the first season the (-P2)-group of calves was grazing a pasture with no detectable trichostrongyles and treated with anthelmintics every second week. The untreated (+P2)-group grazed an Ostertagia ostertagi contaminated pasture. During the second grazing season these 2 original groups grazed together with a new group of first-year grazing calves (-P1) on paddocks infected with O. ostertagi. Parasitological analyses showed that (+P2)-group had negligible egg excretions in the second year in comparison with (-P2) and (-P1). This indicated, that the egg output may be regulated through acquired immunity. The difference in egg excretions was not reflected in the serum pepsinogen levels, which were only slightly elevated for all groups in the second year. Post mortem examination at the end of the experiment showed that only the (-P1)-group harboured relatively high numbers of worms in the abomasa at that time. Antibodies of 3 immunoglobulin classes were investigated: IgA, IgG1 and IgG2. The IgA and IgG1 responses correlated with the presence of developing and adult worms in the abomasa and they remained elevated in the (+P2)-group throughout the experiment, perhaps indicating an involvement of these antibodies in a protective immune response. In the (-P2)-group the IgA and IgG1 showed fast and sharp rises during the second season that most likely were age-related and as such a result of maturation of the immune system. The role of IgG2 is unclear as the IgG2 response was weak in all groups of calves and difficult to relate to the parasitological data.  相似文献   

Standardization of Ultraviolet Irradiation of Channel Catfish Sperm     

J. Michael  Christensen Terrence R.  Tiersch 《Journal of the World Aquaculture Society》1994,25(4):571-575

Gynogenesis is a naturally occurring phenomenon in lower vertebrates in which offspring receive two sets of chromosomes from the female (Dawley 1989). This occurs when development is activated by sperm, but genetic material from the male is not incorporated into the embryo. Normally, haploid offspring result that do not survive to hatching, although in certain instances suppression of meiosis II or first mitosis can result in diploid gynogenetic offspring (Purdom 1993). Artificially induced gynogenesis has been used in the breeding and genetic study of several fishes, including salmonids (Chourrout 1982; Allendorf et al. 1986), tilapia (Don and Avtalion 1988), and channel catfish (Liu et al. 1992). Gynogenesis has been applied to production of monosex populations, isogenic populations, and inbred lines of fish (Ihssen et al. 1990; Tave 1993). Gynogenesis can be induced artificially by irradiating sperm with ultraviolet (UV) radiation to inactivate genetic material. Eggs are fertilized with the irradiated sperm and shocked by temperature or pressure change to restore diploidy.  相似文献