1. |
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2. |
- Edelson, R. A., et al.
(författare)
-
Multiwavelength observations of short-timescale variability in NGC 4151. IV. Analysis of multiwavelength continuum variability
- 1996
-
Ingår i: Astrophysical Journal. - : American Astronomical Society. - 0004-637X .- 1538-4357. ; 470:1, s. 364-377377
-
Tidskriftsartikel (refereegranskat)abstract
- For pt.III see ibid., vol.470, no.1, p.349-63 (1996). Combines data from the three preceding papers in order to analyze the multi wave-band variability and spectral energy distribution of the Seyfert 1 galaxy NGC 4151 during the 1993 December monitoring campaign. The source, which was near its peak historical brightness, showed strong, correlated variability at X-ray, ultraviolet, and optical wavelengths. The strongest variations were seen in medium-energy (~1.5 keV) X-rays, with a normalized variability amplitude (NVA) of 24%. Weaker (NVA=6%) variations (uncorrelated with those at lower energies) were seen at soft gamma-ray energies of ~100 keV. No significant variability was seen in softer (0.1-1 keV) X-ray bands. In the ultraviolet/optical regime, the NVA decreased from 9% to 1% as the wavelength increased from 1275 to 6900 Aring. These data do not probe extreme ultraviolet (1200 Aring to 0.1 keV) or hard X-ray (250 keV) variability. The phase differences between variations in different bands were consistent with zero lag, with upper limits of lsim0.15 day between 1275 Aring and the other ultraviolet bands, lsim0.3 day between 1275 Aring and 1.5 keV, and lsim1 day between 1275 and 5125 Aring. These tight limits represent more than an order of magnitude improvement over those determined in previous multi-wave-band AGN monitoring campaigns. The ultraviolet fluctuation power spectra showed no evidence for periodicity, but were instead well fitted with a very steep, red power law (ales-2.5)
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3. |
- Accomando, E., et al.
(författare)
-
Physics with e + e - linear colliders
- 1998
-
Ingår i: Physics Reports. - 0370-1573. ; 299:1, s. 1-78
-
Tidskriftsartikel (refereegranskat)abstract
- The physics potential of e + e - linear colliders is summarized in this report. These machines are planned to operate in the first phase at a center-of-mass energy of 500 GeV, before being scaled up to about 1 TeV. In the second phase of the operation, a final energy of about 2 TeV is expected. The machines will allow us to perform precision tests of the heavy particles in the Standard Model, the top quark and the electroweak bosons. They are ideal facilities for exploring the properties of Higgs particles, in particular in the intermediate mass range. New vector bosons and novel matter particles in extended gauge theories can be searched for and studied thoroughly. The machines provide unique opportunities for the discovery of particles in supersymmetric extensions of the Standard Model, the spectrum of Higgs particles, the supersymmetric partners of the electroweak gauge and Higgs bosons, and of the matter particles. High precision analyses of their properties and interactions will allow for extrapolations to energy scales close to the Planck scale where gravity becomes significant. In alternative scenarios, i.e. compositeness models, novel matter particles and interactions can be discovered and investigated in the energy range above the existing colliders up to the TeV scale. Whatever scenario is realized in Nature, the discovery potential of e + e - linear colliders and the high precision with which the properties of particles and their interactions can be analyzed, define an exciting physics program complementary to hadron machines.
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4. |
- Crenshaw, D. M., et al.
(författare)
-
Multiwavelength observations of short-timescale variability in NGC 4151. I. Ultraviolet observations
- 1996
-
Ingår i: Astrophysical Journal. - : American Astronomical Society. - 0004-637X .- 1538-4357. ; 470:1, s. 322-335335
-
Tidskriftsartikel (refereegranskat)abstract
- Presents the results of an intensive ultraviolet monitoring campaign on the Seyfert 1 galaxy NGC 4151, as part of an effort to study its short-timescale variability over a broad range in wavelength. The nucleus of NGC 4151 was observed continuously with the International Ultraviolet Explorer for 9.3 days, yielding a pair of LWP and SWP spectra every ~70 minutes, and during 4 hr periods for 4 days prior to and 5 days after the continuous-monitoring period. The sampling frequency of the observations is an order of magnitude higher than that of any previous UV monitoring campaign on a Seyfert galaxy. The continuum fluxes in bands from 1275 to 2688 Aring went through four significant and well-defined ldquoeventsrdquo of duration 2-3 days during the continuous-monitoring period. The authors find that the amplitudes of the continuum variations decrease with increasing wavelength, which extends a general trend for this and other Seyfert galaxies to smaller timescales (i.e., a few days). The continuum variations in all the UV bands are simultaneous to within an accuracy of ~0.15 days, providing a strict constraint on continuum models. The emission-line light curves show only one major event during the continuous monitoring (a slow rise followed by a shallow dip) and do not correlate well with continuum light curves over the short duration of the campaign, because the timescale for continuum variations is apparently smaller than the response times of the emission lines
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5. |
- Dunham, I, et al.
(författare)
-
The DNA sequence of human chromosome 22
- 1999
-
Ingår i: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 402:6761, s. 489-495
-
Tidskriftsartikel (refereegranskat)
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6. |
- Andres, E., et al.
(författare)
-
AMANDA : Status, results and future
- 1999
-
Ingår i: Proceedings, 8th International Workshop, Venice, Italy, February 23-26, 1999. Vol. 1, 2. ; , s. 63-79
-
Konferensbidrag (refereegranskat)abstract
- We review the status of the AMANDA neutrino telescope. We present resultsobtained from the four-string prototype array AMANDA-B4 and describe themethods of track reconstruction and neutrino event separation. We give also firstresults of the analysis of the 10-string detector AMANDA-B10, in particular onatmospheric neutrinos and the search for magnetic monopoles. We sketch thefuture schedule on the way to a cube kilometer telescope at the South Pole,ICECUBE.
|
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7. |
- Halzen, F., et al.
(författare)
-
From the first neutrino telescope, the antarctic muon and neutrino detector array AMANDA, to the IceCube observatory
- 1999
-
Ingår i: Proceedings of the 26th International Cosmic Ray Conference, August 17-25, 1999, Salt Lake City : Invited, Rapporteur, and Highlight Papers. - : American Institute of Physics (AIP). ; , s. 428-431
-
Konferensbidrag (refereegranskat)
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8. |
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9. |
- Andrés, E. C., et al.
(författare)
-
The AMANDA neutrino telescope
- 1999
-
Ingår i: Nuclear physics B, Proceedings supplements. - 0920-5632 .- 1873-3832. ; 77:1-3, s. 474-485
-
Tidskriftsartikel (refereegranskat)abstract
- With an effective telescope area of order 104 m2 for TeV neutrinos, a threshold near ∼50 GeV and a pointing accuracy of 2.5 degrees per muon track, the AMANDA detector represents the first of a new generation of high energy neutrino telescopes, reaching a scale envisaged over 25 years ago. We describe early results on the calibration of natural deep ice as a particle detector as well as on AMANDA's performance as a neutrino telescope.
|
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10. |
- Barwick, S. W., et al.
(författare)
-
Initial results from the AMANDA high-energy neutrino detector
- 1998
-
Ingår i: High-energy physics. Proceedings, 29th International Conference, ICHEP'98, Vancouver, Canada, July 23-29, 1998. Vol. 1, 2. ; , s. 1447-1452
-
Konferensbidrag (refereegranskat)
|
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11. |
- Wischnewski, R., et al.
(författare)
-
The AMANDA neutrino detector
- 1999
-
Ingår i: Nuclear physics B, Proceedings supplements. - : Elsevier. - 0920-5632 .- 1873-3832. ; 75:1-2, s. 412-414
-
Tidskriftsartikel (refereegranskat)abstract
- The first stage of the AMANDA High Energy Neutrino Detector at the South Pole, the 302 PMT array AMANDA-B with an expected effective area for TeV neutrinos of ∼ 104 m2, has been taking data since 1997. Progress with calibration, investigation of ice properties, as well as muon and neutrino data analysis are described. The next stage 20-string detector AMANDA-II with ∼800 PMTs will be completed in spring 2000.
|
|
12. |
- Bay, R. C., et al.
(författare)
-
The AMANDA neutrino telescope and the indirect search for dark matter : AMANDA Colaboration
- 1998
-
Ingår i: Physics reports. - : Elsevier. - 0370-1573 .- 1873-6270. ; 307:1-4, s. 243-252
-
Tidskriftsartikel (refereegranskat)abstract
- With an effective telescope area of order 104m2, a threshold of ~50GeV and a pointing accuracy of 2.5°, the AMANDA detector represents the first of a new generation of high energy neutrino telescopes, reaching a scale envisaged over 25 years ago. We describe its performance, focussing on the capability to detect halo dark matter particles via their annihilation into neutrinos.
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13. |
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14. |
- Miller, T. C., et al.
(författare)
-
Particle astrophysics in antarctica
- 1996
-
Ingår i: International School of Cosmic Ray Astrophysics: 10th Course: Toward the Millennium in Astrophysics: Problems and Prospects 16-26 Jun 1996. Erice, Italy. ; , s. 157-166
-
Konferensbidrag (refereegranskat)
|
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15. |
|
|
16. |
- Andrés, E., et al.
(författare)
-
Status of the AMANDA experiment
- 1999
-
Ingår i: Nuclear physics B, Proceedings supplements. - : Elsevier. - 0920-5632 .- 1873-3832. ; 70:1-3, s. 448-452
-
Tidskriftsartikel (refereegranskat)abstract
- The AMANDA high energy neutrino telescope has successfully been increased in size from four detector strings to ten detector strings during the 1996/1997 season. The first upward going muon-neutrino candidates have been reconstructed from the 1996 year's four-string data. Three new detector strings will be deployed during 1997/1998 to 2350 metres depth.
|
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17. |
- Hunter, D J, et al.
(författare)
-
Non-dietary factors as risk factors for breast cancer, and as effect modifiers of the association of fat intake and risk of breast cancer
- 1997
-
Ingår i: Cancer Causes and Control. - : Springer Science and Business Media LLC. - 0957-5243 .- 1573-7225. ; 8:1, s. 49-56
-
Tidskriftsartikel (refereegranskat)abstract
- To assess more precisely the relative risks associated with established risk factors for breast cancer, and whether the association between dietary fat and breast cancer risk varies according to levels of these risk factors, we pooled primary data from six prospective studies in North America and Western Europe in which individual estimates of dietary fat intake had been obtained by validated food-frequency questionnaires. Based on information from 322,647 women among whom 4,827 cases occurred during follow-up: the multivariate-adjusted risk of late menarche (age 15 years or more compared with under 12) was 0.72 (95 percent confidence interval [CI] = 0.62-0.82); of being postmenopausal was 0.82 (CI = 0.69-0.97); of high parity (three or more births compared with none) was 0.72 (CI = 0.61-0.86); of late age at first birth (over 30 years of age compared with 20 or under) was 1.46 (CI = 1.22-1.75); of benign breast disease was 1.53 (CI = 1.41-1.65); of maternal history of breast cancer was 1.38 (CI = 1.14-1.67); and history of a sister with breast cancer was 1.47 (CI = 1.27-1.70). Greater duration of schooling (more than high-school graduation compared with less than high-school graduation) was associated significantly with higher risk in age-adjusted analyses, but was attenuated after controlling for other risk factors. Total fat intake (adjusted for energy consumption) was not associated significantly with breast cancer risk in any strata of these non-dietary risk factors. We observed a marginally significant interaction between total fat intake and risk of breast cancer according to history of benign breast disease; with fat intake being associated nonsignificantly positively with risk among women with a previous history of benign breast disease; no other significant interactions were observed. Risks for reproductive factors were similar to those observed in case-control studies; relative risks for family history of breast cancer were lower. We found no clear evidence in any subgroups of a major relation between total energy-adjusted fat intake and breast cancer risk.
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18. |
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19. |
- Sims, D. A., et al.
(författare)
-
(γ,n) study of the isovector quadrupole resonance in 40Ca
- 1997
-
Ingår i: Physical Review C: covering nuclear physics. - 2469-9985. ; 55:3, s. 1288-1294
-
Tidskriftsartikel (refereegranskat)abstract
- The forward-to-backward asymmetry of neutrons emitted in the 40Ca(γ,n0) reaction was measured at photon energies in the range of 27–50 MeV. An energy-dependent asymmetry was observed that is interpreted as evidence of interference between the isovector quadrupole resonance and the giant dipole resonance. Data analysis in terms of semiclassical and direct-semidirect models estimate the isovector quadrupole resonance to be at an excitation energy of 31.0±1.5 MeV, with a width of 16.0±1.5 MeV, and exhausting most of the energy-weighted sum rule for the isovector quadrupole resonance.
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20. |
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21. |
- Smith-Warner, Stephanie A., et al.
(författare)
-
Alcohol and breast cancer in women : A pooled analysis of cohort studies
- 1998
-
Ingår i: Journal of the American Medical Association (JAMA). - : American Medical Association (AMA). - 0098-7484 .- 1538-3598. ; 279:7, s. 535-540
-
Tidskriftsartikel (refereegranskat)abstract
- OBJECTIVE: To assess the risk of invasive breast cancer associated with total and beverage-specific alcohol consumption and to evaluate whether dietary and nondietary factors modify the association. DATA SOURCES: We included in these analyses 6 prospective studies that had at least 200 incident breast cancer cases, assessed long-term intake of food and nutrients, and used a validated diet assessment instrument. The studies were conducted in Canada, the Netherlands, Sweden, and the United States. Alcohol intake was estimated by food frequency questionnaires in each study. The studies included a total of 322647 women evaluated for up to 11 years, including 4335 participants with a diagnosis of incident invasive breast cancer. DATA EXTRACTION: Pooled analysis of primary data using analyses consistent with each study's original design and the random-effects model for the overall pooled analyses. DATA SYNTHESIS: For alcohol intakes less than 60 g/d (reported by >99% of participants), risk increased linearly with increasing intake; the pooled multivariate relative risk for an increment of 10 g/d of alcohol (about 0.75-1 drink) was 1.09 (95% confidence interval [CI], 1.04-1.13; P for heterogeneity among studies, .71). The multivariate-adjusted relative risk for total alcohol intakes of 30 to less than 60 g/d (about 2-5 drinks) vs nondrinkers was 1.41 (95% CI, 1.18-1.69). Limited data suggested that alcohol intakes of at least 60 g/d were not associated with further increased risk. The specific type of alcoholic beverage did not strongly influence risk estimates. The association between alcohol intake and breast cancer was not modified by other factors. CONCLUSIONS: Alcohol consumption is associated with a linear increase in breast cancer incidence in women over the range of consumption reported by most women. Among women who consume alcohol regularly, reducing alcohol consumption is a potential means to reduce breast cancer risk.
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22. |
|
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23. |
- Askebjer, P., et al.
(författare)
-
On the age vs depth and optical clarity of deep ice at South Pole
- 1995
-
Ingår i: Journal of Glaciology. - 0022-1430 .- 1727-5652. ; 41:139, s. 445-454
-
Tidskriftsartikel (refereegranskat)abstract
- The first four strings of phototubes for the AMANDA high-energy neutrino observatory are now frozen in place at a depth of 800 to 1000 m in ice at the South Pole. During the 1995-96 season an additional six strings will be deployed at greater depths. Provided absorption, scattering, and refraction of visible light are sufficiently small, the trajectory of a muon into which a neutrino converts can be determined by using the array of phototubes to measure the arrival times of \v{C}erenkov light emitted by the muon. To help in deciding on the depth for implantation of the six new strings, we discuss models of age vs depth for South Pole ice, we estimate mean free paths for scattering from bubbles and dust as a function of depth, and we assess distortion of light paths due to refraction at crystal boundaries and interfaces between air-hydrate inclusions and normal ice. We conclude that the depth interval 1600 to 1800 m will be suitably transparent for the next six AMANDA strings and, moreover, that the interval 1600 to 2100 m will be suitably transparent for a future 1-km 3 observatory except possibly in a region a few tens of meters thick at a depth corresponding to a peak in the dust concentration at 60 kyr BP.
|
|
24. |
- Askebjer, P., et al.
(författare)
-
Optical properties of deep ice at the South Pole : Absorption
- 1997
-
Ingår i: Applied Optics. - : Optical Society of America. - 0003-6935 .- 1539-4522. ; 36:18, s. 4168-4180
-
Tidskriftsartikel (refereegranskat)abstract
- We discuss recent measurements of the wavelength-dependent absorption coefficients in deep South Pole ice. The method uses transit-time distributions of pulses from a variable-frequency laser sent between emitters and receivers embedded in the ice. At depths of 800-1000 m scattering is dominated by residual air bubbles, whereas absorption occurs both in ice itself and in insoluble impurities. The absorption coefficient increases approximately exponentially with wavelength in the measured interval 410-610 nm. At the shortest wavelength our value is approximately a factor 20 below previous values obtained for laboratory ice and lake ice; with increasing wavelength the discrepancy with previous measurements decreases. At ∼415 to ∼500 nm the experimental uncertainties are small enough for us to resolve an extrinsic contribution to absorption in ice: submicrometer dust particles contribute by an amount that increases with depth and corresponds well with the expected increase seen near the Last Glacial Maximum in Vostok and Dome C ice cores. The laser pulse method allows remote mapping of gross structure in dust concentration as a function of depth in glacial ice.
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25. |
- ASKEBJER, P, et al.
(författare)
-
OPTICAL-PROPERTIES OF THE SOUTH-POLE ICE AT DEPTHS BETWEEN 0.8 AND 1 KILOMETER
- 1995
-
Ingår i: SCIENCE. - : AMER ASSOC ADVAN SCIENCE. - 0036-8075. ; 267:5201, s. 1147-1150
-
Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- The optical properties of the ice at the geographical South Pole have been investigated at depths between 0.8 and 1 kilometer. The absorption and scattering lengths of visible light (similar to 515 nanometers) have been measured in situ with the use of th
|
|
26. |
- Askebjer, P., et al.
(författare)
-
UV and optical light transmission properties in deep ice at the South Pole
- 1997
-
Ingår i: Geophysical Research Letters. - : American Geophysical Union (AGU). - 0094-8276 .- 1944-8007. ; 24:11, s. 1355-1358
-
Tidskriftsartikel (refereegranskat)abstract
- Both absorption and scattering of light at wavelengths 410 to 610 nanometers were measured in the South Pole ice at depths 0.8 to 1 kilometer with the laser calibration system of the Antarctic Muon And Neutrino Detector Array (AMANDA). At the shortest wavelengths the absorption lengths exceeded 200 meters - an order of magnitude longer than has been reported for laboratory ice. The absorption shows a strong wavelength dependence while the scattering length is found to be independent of the wavelength, consistent with the hypothesis of a residual density of air bubbles in the ice. The observed linear decrease of the inverse scattering length with depth is compatible with an earlier measurement by the AMANDA collaboration (at ∼515 nanometers).
|
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27. |
- Bergstrom, L., et al.
(författare)
-
The AMANDA experiment : Status and prospects for indirect dark matter detection
- 1996
-
Ingår i: The identification of dark matter. Proceedings, 1st International Workshop, Sheffield, UK, September 8-12, 1996. ; , s. 521-528
-
Konferensbidrag (refereegranskat)abstract
- At the AMANDA South Pole site, four new holes were drilled to depths 2050m to 2180 m and instrumented with 86 photomultipliers (PMTs) at depths1520-2000 m. Of these PMTs 79 are working, with 4-ns timing resolutionand noise rates 300 to 600 Hz. Various diagnostic devices were deployedand are working. An observed factor 60 increase in scattering length anda sharpening of the distribution of arrival times of laser pulses relative tomeasurements at 800-1000 m showed that bubbles are absent below 1500 m.Absorption lengths are 100 to 150 m at wavelengths in the blue and UV to337 nm. Muon coincidences are seen between the SPASE air shower arrayand the AMANDA PMTs at 800-1000 m and 1500-1900 m. The muon trackrate is 30 Hz for 8-fold triggers and 10 Hz for 10-fold triggers. The presentarray is the nucleus for a future expanded array. The potential of AMANDAfor SUSY dark matter search through the detection of high-energy neutrinosfrom the centre of the Sun or Earth is discussed.
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28. |
|
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29. |
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30. |
- Hulth, P. O., et al.
(författare)
-
The AMANDA experiment
- 1996
-
Ingår i: Neutrino '96. Proceedings, 17th International Conference on Neutrino Physics and Astrophysics, Helsinki, Finland, June 13-19, 1996. ; , s. 518-523
-
Konferensbidrag (refereegranskat)abstract
- At the AMANDA South Pole site, four new holes were drilled to depths 2050 m to 2180 m and instrumented with 86 photomultipliers (PMTs) at depths 1520-2000 m. Of these PMTs 79 are working, with 4-ns timing resolution and noise rates 300 to 600 Hz. Various diagnostic devices were deployed and are working. An observed factor 60 increase in scattering length and a sharpening of the distribution of arrival times of laser pulses relative to measurements at 800-1000 m showed that bubbles are absent below 1500 m. Absorption lengths are 100 to 150 m at wavelengths in the blue and UV to 337 nm. Muon coincidences are seen between the SPASE air shower array and the AMANDA PMTs at 800-1000 m and 1500-1900 m. The muon track rate is 30 Hz for 8-fold triggers and 10 Hz for 10-fold triggers. The present array is the nucleus for a future expanded array.
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31. |
- Mock, P. C., et al.
(författare)
-
Status and capabilities of AMANDA-94
- 1995
-
Ingår i: Proceedings, 24th International Conference, Rome, Italy, August 28-September 8, 1995.
-
Konferensbidrag (refereegranskat)
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32. |
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33. |
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34. |
- Askebjer, P., et al.
(författare)
-
AMANDA : status report from the 1993-94 campaign and optical properties of the South Pole ice
- 1995
-
Ingår i: Nuclear physics B, Proceedings supplements. - : Elsevier. - 0920-5632 .- 1873-3832. ; 38:1-3, s. 287-292
-
Tidskriftsartikel (refereegranskat)abstract
- We report the first results of the AMANDA detector. During the antarctic summer 1993-94 four strings were deployed between 0.8 an 1 km depth, each equipped with 20 photomultiplier tubes (PMTs). A laser source was used to investigate the optical properties of the ice in situ. We find that the ice is intrinsically extremely transparent. The measured absorption length is 59 ± 3 m, i.e. comparable with the quality of the ultra-pure water used in the IMB and Kamiokande proton-decay and neutrino experiments [1,2] and more than two times longer than the best value reported for laboratory ice [3]. Due to a residual density of air bubbles at these depths, the motion of photons in the medium is randomized. For spherical, smooth bubbles we find that, at 1 km depth, the average distance between collisions is about 25 cm. The measured inverse scattering length on bubbles decreases linearly with increasing depth in the volume of ice investigated. © 1995 Elsevier Science B.V. All rights reserved.
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35. |
- ASKEBJER, P, et al.
(författare)
-
AMANDA - STATUS-REPORT FROM THE 1993-94 CAMPAIGN AND OPTICAL-PROPERTIES OF THE SOUTH-POLE ICE
- 1995
-
Ingår i: NUCLEAR PHYSICS B. - : ELSEVIER SCIENCE BV. - 0550-3213. ; , s. 287-292
-
Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- We report the first results of the AMANDA detector. During the antarctic summer 1993-94 four strings were deployed between 0.8 an 1 km depth, each equipped with 20 photomultiplier tubes (PMTs). A laser source was used to investigate the optical properties
|
|
36. |
- ASKEBJER, P, et al.
(författare)
-
ON THE AGE VS DEPTH AND OPTICAL CLARITY OF DEEP ICE AT THE SOUTH-POLE
- 1995
-
Ingår i: JOURNAL OF GLACIOLOGY. - : INT GLACIOL SOC. - 0022-1430. ; 41:139, s. 445-454
-
Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- The first four strings of phototubes for the AMANDA high-energy neutrino observatory are now frozen in place at a depth of 800-1000 m in ice at the South Pole. During the 1995-96 season, as many as six more strings will be deployed at greater depths. Prov
|
|
37. |
- Askebjer, P., et al.
(författare)
-
Optical properties of the South Pole ice at depths between 0.8 and 1 kilometer
- 1995
-
Ingår i: Science. - 0036-8075 .- 1095-9203. ; 267:5201, s. 1147-1150
-
Tidskriftsartikel (refereegranskat)abstract
- The optical properties of the ice at the geographical South Pole have been investigated at depths between 0.8 and 1 kilometer. The absorption and scattering lengths of visible light (∼515 nanometers) have been measured in situ with the use of the laser calibration setup of the Antarctic Muon and Neutrino Detector Array (AMANDA) neutrino detector. The ice is intrinsically extremely transparent. The measured absorption length is 59 ± 3 meters, comparable with the quality of the ultrapure water used in the Irvine-Michigan-Brookhaven and Kamiokande proton-decay and neutrino experiments and more than twice as long as the best value reported for laboratory ice. Because of a residual density of air bubbles at these depths, the trajectories of photons in the medium are randomized. If the bubbles are assumed to be smooth and spherical, the average distance between collisions at a depth of 1 kilometer is about 25 centimeters. The measured inverse scattering length on bubbles decreases linearly with increasing depth in the volume of ice investigated.
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38. |
- Askebjer, P, et al.
(författare)
-
UV and optical light transmission properties in deep ice at the South Pole
- 1997
-
Ingår i: GEOPHYSICAL RESEARCH LETTERS. - : AMER GEOPHYSICAL UNION. - 0094-8276. ; 24:11, s. 1355-1358
-
Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Both absorption and scattering of light at wavelengths 410 to 610 nanometers were measured in tile South Pole ice at depths 0.8 to 1 kilometer with the laser calibration system of the Antarctic Muon And Neutrino Detector Array (AMANDA). At the shortest wa
|
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39. |
- Ostrick, J. R., et al.
(författare)
-
Conductivity-type anisotropy in molecular solids
- 1997
-
Ingår i: Journal of Applied Physics. - : American Institute of Physics (AIP). - 0021-8979 .- 1089-7550. ; 81:10, s. 6804-6808
-
Tidskriftsartikel (refereegranskat)abstract
- Thin polycrystalline films of perylenetetracarboxylic dianyhydride (PTCDA), an organic molecular solid, exhibits substantial anisotropies in its electronic transport properties. Only electrons transport in the directions along molecular planes, while mainly holes transport in the direction normal to molecular planes. A series of measurements on both field effect transistors with PTCDA active layers and light emitting diodes with PTCDA transport layers documents the anisotropy seen in the electronic transport in thin films of PTCDA. (C) 1997 American Institute of Physics.
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40. |
- Svensson, Kristian, et al.
(författare)
-
The paternal allele of the H19 gene is silenced in a stepwise manner duringearly mouse development: the acetylation status of histones mya be involved in the generation of variegated expression patter
- 1998
-
Ingår i: Development. - 0950-1991 .- 1477-9129. ; 125:1, s. 61-69
-
Tidskriftsartikel (refereegranskat)abstract
- Transcriptional silencing can reflect heritable, epigenetic inactivation of genes, either singly or in groups, during the life-time of an organism. This phenomenon is exemplified by parent-of-origin-specific inactivation events (genomic imprinting) for a subset of mammalian autosomal genes, such as H19. Very little is known, however, about the timing and mechanism(s) of silencing of the paternal H19 allele during mouse development. Using a novel in situ approach, we present evidence that the silencing of the paternal H19 allele is progressive in the trophectodermal lineage during early mouse development and generates variegated expression patterns. The silencing process apparently involves recruitment of histone deacetylases since the mosaic paternal-specific H19 expression reappears in trichostatin A-treated mouse conceptuses, undergoing in vitro organogenesis. Moreover, the paternal H19 alleles of PatDup.d7 placentas, in which a region encompassing the H19 locus of chromosome 7 is bipaternally derived, partially escape the silencing process and are expressed in a variegated manner. We suggest that allele-specific silencing of H19 share some common features with chromatin-mediated silencing in position-effect variegation.
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41. |
- Berglund, B E, et al.
(författare)
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Sweden
- 1996
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Annan publikation (övrigt vetenskapligt/konstnärligt)
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42. |
- Franklin, Gary C., et al.
(författare)
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An Inr-containing sequence flanking the TATA box of the human c-sis (PDGF-B) proto-oncogene promoter functions in cis as a co-activator for its intronic enhancer
- 1995
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Ingår i: Oncogene. - 0950-9232 .- 1476-5594. ; 11:9, s. 1873-1884
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- High-level activity of the human PDGF-B promoter in choriocarcinoma cell lines depends upon an atypical, intronic enhancer-like element which does not function with heterologous promoters tested. An extensive series of mutant PDGF-B promoter-driven constructs identified a sequence flanking the TATA box which is required specifically for enhancer-mediated transcription in human choriocarcinoma cell lines. This element, which we here term an enhancer-dependent cis co-activator (EDC) contains an Inr (initiator) consensus sequence upstream of the TATA box which is required, but not sufficient for its function. Requirement for the EDC is cell type-specific, since it was dispensable for enhancer-mediated transcription in a human breast cancer cell line. Although it lies within the region defined, the TATA box itself is not required for EDC function, or for basal promoter function which may derive from a second Inr-like sequence situated at the transcriptional start site. These observations indicate that interactions between some promoter and enhancer elements may be more complex than that generally described for 'classical' enhancer systems and may suggest an additional function for the initiator motif.
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43. |
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