2,108 research outputs found
Climate or rural development policy?
Being heavily energy dependent, it is not much of a surprise that Europe pays special attention to reducing the use of fossil fuels. Each one of the ten new member states is characterized by relatively low per capita energy consumption and relatively low energy efficiency, and the share of renewables in their energy mix tends to be low, too. The paper examines the problem when policy measures create a decrease in environmental capital instead of an increase. In this case it hardly seems justified to talk about environmental protection. The authors describe a case of a Hungarian rapeseed oil mill which would not be of too much interest on its own but given that almost all similar plants went bankrupt, there are some important lessons to learn from its survival. The enterprise the authors examined aimed at establishing a micro-regional network. They completed a brown-field development to establish a small plant on the premises of a former large agricultural cooperative. By partnering with the former employees and suppliers of the sometime cooperative, they enjoyed some benefits which all the other green-field businesses focusing on fuel production could not. The project improved food security, energy security and population retention as well
Frequency evaluation of the doubly forbidden transition in bosonic Yb
We report an uncertainty evaluation of an optical lattice clock based on the
transition in the bosonic isotope Yb by use
of magnetically induced spectroscopy. The absolute frequency of the
transition has been determined through comparisons
with optical and microwave standards at NIST. The weighted mean of the
evaluations is (Yb)=518 294 025 309 217.8(0.9) Hz. The uncertainty
due to systematic effects has been reduced to less than 0.8 Hz, which
represents in fractional frequency.Comment: 4 pages, 3 figure -Submitted to PRA Rapid Communication
Measurement of excited-state transitions in cold calcium atoms by direct femtosecond frequency-comb spectroscopy
We apply direct frequency-comb spectroscopy, in combination with precision cw
spectroscopy, to measure the transition
frequency in cold calcium atoms. A 657 nm ultrastable cw laser was used to
excite atoms on the narrow ( Hz) clock transition, and the direct output of the frequency comb was
used to excite those atoms from the state to the state. The resonance of this second stage was detected by observing a
decrease in population of the ground state as a result of atoms being optically
pumped to the metastable states. The transition frequency is measured to be kHz; which is an improvement by almost four orders of magnitude over
the previously measured value. In addition, we demonstrate spectroscopy on
magnetically trapped atoms in the state.Comment: 4 pages 5 figure
Kilohertz-resolution spectroscopy of cold atoms with an optical frequency comb
We have performed sub-Doppler spectroscopy on the narrow intercombination
line of cold calcium atoms using the amplified output of a femtosecond laser
frequency comb. Injection locking of a 657-nm diode laser with a femtosecond
comb allows for two regimes of amplification, one in which many lines of the
comb are amplified, and one where a single line is predominantly amplified. The
output of the laser in both regimes was used to perform kilohertz-level
spectroscopy. This experiment demonstrates the potential for high-resolution
absolute-frequency spectroscopy over the entire spectrum of the frequency comb
output using a single high-finesse optical reference cavity.Comment: 4 pages, 4 Figure
Quenched Narrow-Line Laser Cooling of 40Ca to Near the Photon Recoil Limit
We present a cooling method that should be generally applicable to atoms with
narrow optical transitions. This technique uses velocity-selective pulses to
drive atoms towards a zero-velocity dark state and then quenches the excited
state to increase the cooling rate. We demonstrate this technique of quenched
narrow-line cooling by reducing the 1-D temperature of a sample of neutral 40Ca
atoms. We velocity select and cool with the 1S0(4s2) to 3P1(4s4p) 657 nm
intercombination line and quench with the 3P1(4s4p) to 1S0(4s5s)
intercombination line at 553 nm, which increases the cooling rate eight-fold.
Limited only by available quenching laser power, we have transferred 18 % of
the atoms from our initial 2 mK velocity distribution and achieved temperatures
as low as 4 microK, corresponding to a vrms of 2.8 cm/s or 2 recoils at 657 nm.
This cooling technique, which is closely related to Raman cooling, can be
extended to three dimensions.Comment: 5 pages, 4 figures; Submitted to PRA Rapid Communication
Stemming and best practice in the mining industry : a literature review
In 2015, after amendments to the explosives regulations, stemming became a mandatory activity for all
South African mining operations. There are, however, circumstances in which it is thought stemming
has an adverse impact on the blasting outcome. Some of these circumstances include blasting in
hot holes, in reactive ground, or when blasting a pre-split. In order to determine when stemming is
necessary, its role in the control of adverse blasting phenomena and impact on explosive performance
were reviewed. Stemming was found to play a significant role in the fragmentation process and burden
movement. Additionally, stemming significantly influences the control of flyrock, air-blast, and toxic
fume generation. The review of the literature indicates some motivation for not using stemming for presplit,
trim, hot hole, and reactive ground blasting, provided the benefits associated with not stemming
the holes outweigh the risks of stemming them. Best practice for stemming from the literature indicates
a stemming length of 0.7 Ă burden is best for larger hole diameters, and 20 to 30 Ă Ă for smaller hole
diameters. Crushed aggregate appears to be the most effective stemming material. The South African
explosives regulations pertaining to stemming were found to be consistent with those of Australia and
the USA.http://www.saimm.co.za/journal-papersam2022Mining Engineerin
Absolute Frequency Measurements of the Hg^+ and Ca Optical Clock Transitions with a Femtosecond Laser
The frequency comb created by a femtosecond mode-locked laser and a
microstructured fiber is used to phase coherently measure the frequencies of
both the Hg^+ and Ca optical standards with respect to the SI second as
realized at NIST. We find the transition frequencies to be f_Hg=1 064 721 609
899 143(10) Hz and f_Ca=455 986 240 494 158(26) Hz, respectively. In addition
to the unprecedented precision demonstrated here, this work is the precursor to
all-optical atomic clocks based on the Hg^+ and Ca standards. Furthermore, when
combined with previous measurements, we find no time variations of these atomic
frequencies within the uncertainties of |(df_Ca/dt)/f_Ca| < 8 x 10^{-14}
yr^{-1}, and |(df_Hg/dt)/f_Hg|< 30 x 10^{-14} yr^{-1}.Comment: 6 pages, including 4 figures. RevTex 4. Submitted to Phys. Rev. Let
Laser frequency stabilization to a single ion
A fundamental limit to the stability of a single-ion optical frequency
standard is set by quantum noise in the measurement of the internal state of
the ion. We discuss how the interrogation sequence and the processing of the
atomic resonance signal can be optimized in order to obtain the highest
possible stability under realistic experimental conditions. A servo algorithm
is presented that stabilizes a laser frequency to the single-ion signal and
that eliminates errors due to laser frequency drift. Numerical simulations of
the servo characteristics are compared to experimental data from a frequency
comparison of two single-ion standards based on a transition at 688 THz in
171Yb+. Experimentally, an instability sigma_y(100 s)=9*10^{-16} is obtained in
the frequency difference between both standards.Comment: 15 pages, 5 figures, submitted to J. Phys.
SURVEILLANCE OF SELECTED DISEASES IN FREE-RANGING ELK (\u3ci\u3eCERVUS ELAPHUS NELSONI\u3c/i\u3e) IN NEBRASKA, 1995-2009
Sera samples were collected from 21 free-ranging, captured female elk (Cervus elaphus nelsoni) in 1995- 96, and tissue and sera samples were collected from 415 hunter-harvested elk from 1995 to 2006 and tested for selected diseases. Titers for Anaplasma marginale were detected in 81 of 436 (19%) elk. Occurrence of antibodies to anaplasmosis increased from 4 to 40 elk from 2002 to 2006. Titers for bovine viral diarrhea virus (BVDV) were detected in 18 of 346 (5%) samples. Titers for Leptospira interrogans serovars were detected in 21 of 289 (7%) of samples from 1995 to 2004. Titers for bluetongue virus (BTV) and epizootic hemorrhagic disease virus (EHDV) were detected in 65 of 370 (18%) sampled elk during 1995-2006. Biologists collected obex tissues from 566 elk from 1997 to 2009 and found evidence of chronic wasting disease (CWO) in one elk in 2009. No brucellosis was detected. Due to the prevalence of several diseases in elk in Nebraska, we recommend that surveillance efforts continue
SURVEILLANCE OF SELECTED DISEASES IN FREE-RANGING ELK (\u3ci\u3eCERVUS ELAPHUS NELSONI\u3c/i\u3e) IN NEBRASKA, 1995-2009
Sera samples were collected from 21 free-ranging, captured female elk (Cervus elaphus nelsoni) in 1995- 96, and tissue and sera samples were collected from 415 hunter-harvested elk from 1995 to 2006 and tested for selected diseases. Titers for Anaplasma marginale were detected in 81 of 436 (19%) elk. Occurrence of antibodies to anaplasmosis increased from 4 to 40 elk from 2002 to 2006. Titers for bovine viral diarrhea virus (BVDV) were detected in 18 of 346 (5%) samples. Titers for Leptospira interrogans serovars were detected in 21 of 289 (7%) of samples from 1995 to 2004. Titers for bluetongue virus (BTV) and epizootic hemorrhagic disease virus (EHDV) were detected in 65 of 370 (18%) sampled elk during 1995-2006. Biologists collected obex tissues from 566 elk from 1997 to 2009 and found evidence of chronic wasting disease (CWO) in one elk in 2009. No brucellosis was detected. Due to the prevalence of several diseases in elk in Nebraska, we recommend that surveillance efforts continue
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