902 research outputs found
Influence of starvation on selected temperatures in the young of bream, roach and perch [Translation from: Informatsionnyi Byulleten Biologiya Vnutrennikh Vod No.50, 45-47, 1981]
Works devoted to the influence of starvation on temperature selection by fishes are few and their conclusions are contradictory. This study determined the influence of brief, up to 14 days, starvation on temperature selection by young fishes. The experiments were carried out in August-September 1976 on fingerling bream (Abramis brama L.), roach (Rutilus rutilus L.) and perch (Perca fluviatilis L.) with body lengths of 3-5 cm and weight 0.5-1.2 g. The young fish were caught in the littoral by seine-nets or small drag-nets. Immediately after catching the fish they were put in acclimatization boxes. The period of acclimatization did not exceed 2 days for bream and roach at a temperature of 20 °C and 6 days for perch at 17 °C. Before the start of the experiment and for the first 10 days of the experiment the fish were fed with oligochaetes, earthworms and daphnia, after that feeding discontinued. At the end of a 10-14 day period the giving of food was resumed. The study concludes that the experiments have shown that in the summer season the factor of starvation significantly changes the reaction to the gradient of temperature in young cyprihids - roach and bream
Multi-objective Optimizations of a Novel Cryo-cooled DC Gun Based Ultra Fast Electron Diffraction Beamline
We present the results of multi-objective genetic algorithm optimizations of
a potential single shot ultra fast electron diffraction beamline utilizing a
225 kV dc gun with a novel cryocooled photocathode system and buncher cavity.
Optimizations of the transverse projected emittance as a function of bunch
charge are presented and discussed in terms of the scaling laws derived in the
charge saturation limit. Additionally, optimization of the transverse coherence
length as a function of final rms bunch length at sample location have been
performed for three different sample radii: 50, 100, 200 microns, for two final
bunch charges: 100k and 1000k electrons. Analysis of the solutions is
discussed, as are the effects of disorder induced heating. In particular, a
coherence length per rms spot size of 0.27 nm/micron was obtained for a final
bunch charge of 100k electrons and final rms bunch length of approximately 100
fs. For a final charge of 1000k electrons the cryogun produces a coherence
length per rms spot size of 0.1 nm/micron for an rms bunch length of 100-200 fs
and final spot size of 50 micron. These results demonstrate the viability of
using genetic algorithms in the design and operation of ultrafast electron
diffraction beamlines
The Whirlpool Splitting
AbstractAn unusual phenomenon called “whirlpool splitting” by analogy with an axe splitting wood logs was experimentally observed. In this experiment, a metal ruler, set vertically on the bottom of the aquarium on the hole axis during flowing out of water has led to the separation of a whirlpool into two formed on both sides of the rule and existed until the end of draining. The paper describes some results of experiments based on the research of this phenomeno
Contactless Measurement of Angular - Speed
The control technology has been improved to enormous scales so far. People are trying to
apply control over everything they do, so that the level of accuracy and efficiency
increase. The simplest form of control could be a control of a rotating shaft. We might
want to keep its speed stable at some rps (rounds per second). This can be achieved in
numerous methods. Regardless of any method chosen, the first step to achieve this goal
would always be being able to measure the speed and then to apply control measures to
it.
In this project, I aminvestigating contactless measurement ofangular speed of a rotating
shaft. My main objective is to demonstrate how to measure the angular speed of a
rotating shaft contactlessly. Contactless measurement of angular speed is particularly
critical when dealing with load-sensitive devices such as mobile antennas.
I am achieving the contactless measurement through using IR (infrared) emitter-detector
circuitry. The IR pair generates pulses, which are galvanized by the rotation of the shaft.
Slots on a disk mounted to the shaft permits light transmission between IR emitter and
detector, which are placed on both sides of the disk. Hence, when the disk rotates it is
possible to get stream of pulses from the circuitry.
I used a PIC microcontroller to accept the pulses and obtain the angular speed in terms of
rps. This value is then displayed on 7-segment LEDs.
Lastly, this project involved a lot of microprocessor concepts. I tried my best to present
concepts involvedas comprehensible as possible. I expectthe reader to have no difficulty
while reading it
Effect of nano-scale surface roughness on transverse energy spread from GaAs photocathodes
High quantum yield, low transverse energy spread and prompt response time
make GaAs activated to negative electron affnity, an ideal candidate for a
photocathode in high brightness photoinjectors. Even after decades of
investigation, the exact mechanism of electron emission from GaAs is not well
understood. We show that a nanoscale surface roughness can affect the
transverse electron spread from GaAs by nearly an order of magnitude and
explain the seemingly controversial experimental results obtained so far. This
model can also explain the measured dependence of transverse energy spread on
the wavelength of incident light.Comment: 3pages, 3figure
Comparison of DC and SRF Photoemission Guns For High Brightness High Average Current Beam Production
A comparison of the two most prominent electron sources of high average
current high brightness electron beams, DC and superconducting RF photoemission
guns, is carried out using a large-scale multivariate genetic optimizer
interfaced with space charge simulation codes. The gun geometry for each case
is varied concurrently with laser pulse shape and parameters of the downstream
beamline elements of the photoinjector to obtain minimum emittance as a
function of bunch charge. Realistic constraints are imposed on maximum field
values for the two gun types. The SRF and DC gun emittances and beam envelopes
are compared for various values of photocathode thermal emittance. The
performance of the two systems is found to be largely comparable provided low
intrinsic emittance photocathodes can be employed
Cold electron beams from cryo-cooled, alkali antimonide photocathodes
In this letter we report on the generation of cold electron beams using a
Cs3Sb photocathode grown by co-deposition of Sb and Cs. By cooling the
photocathode to 90 K we demonstrate a significant reduction in the mean
transverse energy validating the long standing speculation that the lattice
temperature contribution limits the mean transverse energy or thermal emittance
near the photoemission threshold, opening new frontiers in generating
ultra-bright beams. At 90 K, we achieve a record low thermal emittance of 0.2
m (rms) per mm of laser spot diameter from an ultrafast (sub-picosecond)
photocathode with quantum efficiency greater than using a
visible laser wavelength of 690 nm
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