1,501 research outputs found
Complete Photoionization Experiments via Ultrafast Coherent Control with Polarization Multiplexing II: Numerics & Analysis Methodologies
The feasibility of complete photoionization experiments, in which the full
set of photoionization matrix elements are determined, using multiphoton
ionization schemes with polarization-shaped pulses has recently been
demonstrated [Hockett et. al., Phys. Rev. Lett. 112, 223001 (2014)]. Here we
extend on our previous work to discuss further details of the numerics and
analysis methodology utilised, and compare the results directly to new
tomographic photoelectron measurements, which provide a more sensitive test of
the validity of the results. In so doing we discuss in detail the physics of
the photoionziation process, and suggest various avenues and prospects for this
coherent multiplexing methodology
Maximum information photoelectron metrology
Photoelectron interferograms, manifested in photoelectron angular
distributions (PADs), are a high-information, coherent observable. In order to
obtain the maximum information from angle-resolved photoionization experiments
it is desirable to record the full, 3D, photoelectron momentum distribution.
Here we apply tomographic reconstruction techniques to obtain such 3D
distributions from multiphoton ionization of potassium atoms, and fully analyse
the energy and angular content of the 3D data. The PADs obtained as a function
of energy indicate good agreement with previous 2D data and detailed analysis
[Hockett et. al., Phys. Rev. Lett. 112, 223001 (2014)] over the main spectral
features, but also indicate unexpected symmetry-breaking in certain regions of
momentum space, thus revealing additional continuum interferences which cannot
otherwise be observed. These observations reflect the presence of additional
ionization pathways and, most generally, illustrate the power of maximum
information measurements of this coherent observable
Strong impact of light induced conical intersections on the spectrum of diatomic molecules
We show that dressing of diatomic molecules by running laser waves gives rise
to conical intersections (CIs). Due to presence of such CIs, the rovibronic
molecular motions are strongly coupled. A pronounced impact of the CI on the
spectrum of molecule is demonstrated via numerical calculation for weak
and moderate laser intensity, and an experiment is suggested on this basis. The
position of the light induced CI and the strength of its non-adiabatic
couplings can be chosen by changing the frequency and intensity of the used
running laser wave. This offers new possibilities to control the photo-induced
rovibronic molecular dynamics.Comment: 4 pages, 7 figure
Complete Solving for Explicit Evaluation of Gauss Sums in the Index 2 Case
Let be a prime number, for some positive integer , be a
positive integer such that , and let \k be a primitive
multiplicative character of order over finite field \fq. This paper
studies the problem of explicit evaluation of Gauss sums in "\textsl{index 2
case}" (i.e. f=\f{\p(N)}{2}=[\zn:\pp], where \p(\cd) is Euler function).
Firstly, the classification of the Gauss sums in index 2 case is presented.
Then, the explicit evaluation of Gauss sums G(\k^\la) (1\laN-1) in index 2
case with order being general even integer (i.e. N=2^{r}\cd N_0 where
are positive integers and is odd.) is obtained. Thus, the
problem of explicit evaluation of Gauss sums in index 2 case is completely
solved
The Physiological and Genetic Factors Underpinning the Response to Muscle Damaging Exercise
It is often observed that there is a high individual variability in the response to exercise-induced muscle damage (EIMD), even when tested in a homogeneous cohort accounting for age, sex, ethnicity and physical activity. The response to EIMD is very complex as several tissues, including skeletal muscle fibres, the extra-cellular matrix (ECM), and tendon, play a potential role in the damage response. Therefore, the overall aim of this PhD thesis was to investigate the physiological and genetic factors underpinning the response to muscle damaging exercise. For that, the following objectives were (i) to comprehensively assess the physiological mechanisms and recovery pattern of neuromuscular fatigue of the hamstring muscle group following an intermittent sprint (IS) intervention; (ii) to investigate inter-individual differences in skeletal muscle repair/recovery after an artificial wounding (scratch) assay using of primary human skeletal muscle cells in vitro; (iii) to ascertain whether multiple genetic variations, which are linked to varying tissues, forming a polygenic profile could distinguish between high and low responders following muscle damage in vivo and in vitro; and (iv) to assess whether a genetic profile is linked with the response to both EIMD and chronic resistance exercise. The methodological and analytical approaches utilised in this thesis identified a number of important, novel and impactful findings. Following IS, the impaired hamstring muscle function and delayed recovery is probably caused primarily by damage to the contractile tissue, and participants with a greater force generating capacity (larger physiological cross-sectional area) of the biceps femoris long head were less susceptible to hamstring strength loss immediately after IS, providing evidence that the structure of the muscle protects it against peripheral fatigue/damage. The in vitro study showed that skeletal muscles with an increased number of stem cells of the connective tissue (fibroblasts) might have a better capacity to reorganise the complex ECM, which results in a faster muscle strength recovery after muscle damaging exercise. However, a larger number of active muscle stem cells (myoblasts) seems to be important for the latter stage of muscle regeneration. Individuals possessing a non-preferential genetic profile demonstrated increased rate of muscle damage biomarkers than individuals with a preferential genetic profile. Lastly, we calculated a second polygenic profile which was linked with both the EIMD and the chronic resistance exercise response. These polygenic profiles may be used to anticipate an individualâs response/adaptation to EIMD and to chronic resistance exercise, thus enabling resistance exercise to be prescribed on a personalised level to improve muscle health and function
Scaling graphs of heart rate time series in athletes demonstrate the VLF, LF and HF regions
Scaling analysis of heart rate time series has emerged as an useful tool for
assessment of autonomic cardiac control. We investigate the heart rate time
series of ten athletes (five males and five females), by applying detrended
fluctuation analysis (DFA). High resolution ECGs are recorded under
standardized resting conditions over 30 minutes and subsequently heart rate
time series are extracted and artefacts filtered. We find three distinct
regions of scale-invariance, which correspond to the well-known VLF, LF, and HF
bands in the power spectra of heart rate variability. The scaling exponents
alpha are alphaHF: 1.15 [0.96-1.22], alphaLF: 0.68 [0.57-0.84], alphaVLF:
0.83[0.82-0.99]; p<10^-5). In conclusion, DFA scaling exponents of heart rate
time series should be fitted to the VLF, LF, and HF ranges, respectively
TRIM63 (MuRF-1) Gene Polymorphism is Associated with Biomarkers of Exercise-Induced Muscle Damage
Unaccustomed strenuous exercise can lead to muscle strength loss, inflammation and delayed onset muscle soreness, which may be influenced by genetic variation. We investigated if a missense single nucleotide polymorphism (A>G, rs2275950) within the TRIM63 gene (encoding MuRF-1 and potentially affecting titin mechanical properties) was associated with the variable response to unaccustomed eccentric exercise. Sixty-five untrained, healthy participants (genotyped for rs2275950: AA, AG and GG) performed 120 maximal eccentric knee extensions (ECC) to induce muscle damage. Isometric and isokinetic maximal voluntary knee extension contractions (MVCs) and muscle soreness were assessed before, immediately after, and 48h after ECC. AA homozygotes were consistently stronger [baseline isometric MVC: 3.23±0.92 Nm/kg (AA) vs. 2.09±0.67 Nm/kg (GG); p=0.006] and demonstrated less muscle soreness over time (p=0.022) compared to GG homozygotes. This may be explained by greater titin stiffness in AA homozygotes, leading to intrinsically stronger muscle fibers that are more resistant to eccentric damaging contractions
Hidden Markov models based on symbolic dynamics for statistical modeling of cardiovascular control in hypertensive pregnancy disorders
Copyright © 2006 IEEEDiscrete hidden Markov models (HMMs) were applied to classify pregnancy disorders. The observation sequence was generated by transforming RR and systolic blood pressure time series using symbolic dynamics. Time series were recorded from 15 women with pregnancy-induced hypertension, 34 with preeclampsia and 41 controls beyond 30th gestational week. HMMs with five to ten hidden states were found to be sufficient to characterize different blood pressure variability, whereas significant classification in RR-based HMMs was found using fifteen hidden states. Pregnancy disorders preeclampsia and pregnancy induced hypertension revealed different patho-physiological autonomous regulation supposing different etiology of both disorders.V. Baier, M. Baumert, P. Caminal, M. VallverdĂș, R. Faber, and A. Vos
Coherent strong-field control of multiple states by a single chirped femtosecond laser pulse
We present a joint experimental and theoretical study on strong-field
photo-ionization of sodium atoms using chirped femtosecond laser pulses. By
tuning the chirp parameter, selectivity among the population in the highly
excited states 5p, 6p, 7p and 5f, 6f is achieved. Different excitation pathways
enabling control are identified by simultaneous ionization and measurement of
photoelectron angular distributions employing the velocity map imaging
technique. Free electron wave packets at an energy of around 1 eV are observed.
These photoelectrons originate from two channels. The predominant 2+1+1
Resonance Enhanced Multi-Photon Ionization (REMPI) proceeds via the strongly
driven two-photon transition , and subsequent
ionization from the states 5p, 6p and 7p whereas the second pathway involves
3+1 REMPI via the states 5f and 6f. In addition, electron wave packets from
two-photon ionization of the non-resonant transiently populated state 3p are
observed close to the ionization threshold. A mainly qualitative five-state
model for the predominant excitation channel is studied theoretically to
provide insights into the physical mechanisms at play. Our analysis shows that
by tuning the chirp parameter the dynamics is effectively controlled by dynamic
Stark-shifts and level crossings. In particular, we show that under the
experimental conditions the passage through an uncommon three-state "bow-tie"
level crossing allows the preparation of coherent superposition states
Coherent Optimal Control of Multiphoton Molecular Excitation
We give a framework for molecular multiphoton excitation process induced by
an optimally designed electric field. The molecule is initially prepared in a
coherent superposition state of two of its eigenfunctions. The relative phase
of the two superposed eigenfunctions has been shown to control the optimally
designed electric field which triggers the multiphoton excitation in the
molecule. This brings forth flexibility in desiging the optimal field in the
laboratory by suitably tuning the molecular phase and hence by choosing the
most favorable interfering routes that the system follows to reach the target.
We follow the quantum fluid dynamical formulation for desiging the electric
field with application to HBr molecule.Comment: 5 figure
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