Low-temperature antihydrogen atoms are an effective tool to probe the validity of the fundamental laws of Physics, for example the Weak Equivalence Principle (WEP) for antimatter, and -generally ...speaking- it is obvious that colder atoms will increase the level of precision.
After the first production of cold antihydrogen in 2002 1, experimental efforts have substantially progressed, with really competitive results already reached by adapting to cold antiatoms some well-known techniques pre- viously developed for ordinary atoms. Unfortunately, the number of antihydrogen atoms that can be produced in dedicated experiments is many orders of magnitude smaller than of hydrogen atoms, so the development of novel techniques to enhance the production of antihydrogen with well defined (and possibly controlled) conditions is essential to improve the sensitivity.
We present here some experimental results achieved by the AEgIS Collaboration, based at the CERN AD (Antiproton Decelerator) on the production of antihydrogen in a pulsed mode where the production time of 90% of atoms is known with an uncertainty of ~ 250 ns 2. The pulsed antihydrogen source is generated by the charge-exchange reaction between Rydberg positronium (
Ps*
) and an antiproton (
p¯
):
p¯
+
P
s
*
→
H¯
* +
e
−
, where
Ps*
is produced via the implantation of a pulsed positron beam into a mesoporous silica target, and excited by two consecutive laser pulses, and antiprotons are trapped, cooled and manipulated in Penning-Malmberg traps. The pulsed production (which is a major milestone for AEgIS) makes it possible to select the antihydrogen axial temperature and opens the door for the tuning of the antihydrogen Rydberg states, their de-excitation by pulsed lasers and the manipulation through electric field gradients.
In this paper, we present the results achieved by AEgIS in 2018, just before the Long Shutdown 2 (LS2), as well as some of the ongoing improvements to the system, aimed at exploiting the lower energy antiproton beam from ELENA 3.
Established theory addresses the idea that herbivory can have positive feedbacks on nutrient flow to plants. Positive feedbacks likely emerge from a greater availability of organic carbon that primes ...the soil by supporting nutrient turnover through consumer and especially microbially-mediated metabolism in the detrital pool. We developed an entirely novel stoichiometric model that demonstrates the mechanism of a positive feedback. In particular, we show that sloppy or partial feeding by herbivores increases detrital carbon and nitrogen allowing for greater nitrogen mineralization and nutritive feedback to plants. The model consists of differential equations coupling flows among pools of: plants, herbivores, detrital carbon and nitrogen, and inorganic nitrogen. We test the effects of different levels of herbivore grazing completion and of the stoichiometric quality (carbon to nitrogen ratio, C:N) of the host plant. Our model analyses show that partial feeding and plant C:N interact because when herbivores are sloppy and plant biomass is diverted to the detrital pool, more mineral nitrogen is available to plants because of the stoichiometric difference between the organisms in the detrital pool and the herbivore. This model helps to identify how herbivory may feedback positively on primary production, and it mechanistically connects direct and indirect feedbacks from soil to plant production.
•The detection of the exremely weak A1Sigma+b˜3Pi→a3Sigmatransitions in laser-induced fluorescence of RbCs.•The scalar- and full-relativistic ab initio calculations of the transition dipole ...moments.•The comparison of the experimental and theoretical branching ratios of transitions to the triplet and singlet ground states.•The explanation of pecularities in the doublet progressions to the triplet ground state.
We observed the A1Σ+∼b3Π→a3Σ+/X1Σ+laser-induced fluorescence (LIF) of the RbCs molecule excited from the ground X1Σ+state by the Ti:Sapphire laser. The LIF spectra from the common perturbed levels of the singlet-triplet A ∼ b complex was recorded by the Fourier-transform (FT) spectrometer with the instrumental resolution of 0.03 cm−1. The relative intensity distribution in the rotationally resolved A∼b→a3Σ+(va)/X1Σ+(vX)progressions was measured, and their branching ratio was found to be about of 1÷5×10−4in the bound region of the a3Σ+and X1Σ+states. The experiment was complemented with the scalar- and full-relativistic calculations of the A/b−X/atransition dipole moments (TDMs) as functions of internuclear distance. The relative systematic error in the resulting ab initio TDM functions evaluated for the strong A−Xtransition was estimated as few percent in the energy region, where the experimental LIF intensities are relevant. The relative spectral sensitivity of the FT registration system, operated with the InGaAs diode detector and CaF beam-splitter, was calibrated in the range 6 500, 12 000 cm−1by a comparison of experimental intensities in the long A ∼ b → X(vX) LIF progressions of the K2 and KCs molecules with their theoretical counterparts evaluated using the ab initioA−XTDMs. Both experimental and theoretical transition probabilities can be employed to improve the stimulated Raman adiabatic passage process, a → A ∼ b → X, which is exploited for a laser assembling of ultracold RbCs molecules.
•673 experimental term values belonging to both e/f -components of the c3ΣΩ=1+ state of KCs were determined with about 0.01 cm−1 accuracy applying high resolution Fouriertransform spectroscopy.•High ...fidelity relativistic coupled cluster calculation on the electronic structure of the KCs low-lying states was performed.•Semi-empirical point-wise interatomic potential was reconstructed for the c3Σ1+ state.•Ω -doubling effect in the c3Σ1+ state was investigated.•Radiative properties of the c3Σ+ state were simulated for the lowest vibrational vc≤22 levels.
The Ti:Saphire laser operated within 13800 - 11800 cm−1 range was used to excite the c3Σ+ state of KCs molecule directly from the ground X1Σ+ state. The laser-induced fluorescence (LIF) spectra of the c3Σ+→a3Σ+ transition were recorded with Fourier-transform spectrometer within 8000 to 10000 cm−1 range. Overall 673 rovibronic term values belonging to both e/f-components of the c3Σ+(Ω=1±) state of 39KCs, covering vibrational levels from v = 0 to about 45, and rotational levels J∈11,149 were determined with the accuracy of about 0.01 cm−1; among them 7 values for 41KCs. The experimental term values with v∈0,22 were involved in a direct point-wise potential reconstruction for the c3Σ+(Ω=1±) state, which takes into account the Ω-doubling effect caused by the spin-rotational interaction with the nearby c3Σ+(Ω=0−) state. The analysis and interpretation were facilitated by the fully-relativistic coupled cluster calculation of the potential energy curves for the B1Π, c3Σ+, and b3Π states, as well as of spin-forbidden c−X and spin-allowed c−a transition dipole moments; radiative lifetimes and vibronic branching ratios were calculated. A comparison of relative intensity distributions measured in vibrational c→a LIF progressions with their theoretical counterparts unambiguously confirms the vibrational assignment suggested in J. Szczepkowski, et al., JQSRT, 204, 133–137 (2018).
•High-resolution spectroscopy.•Coupled channels deperturbation.•Hyperfine structure.•Relativistic ab initio calculations.
Laser-induced fluorescence spectra of the c3Σ+(vc,Jc=Nc)→a3Σ+(va,Na=Jc±1) ...transitions excited from the ground X1Σ+ state of 39K133Cs molecule were recorded with Fourier-transform spectrometer IFS125-HR (Bruker) at the highest achievable spectral resolution of 0.0063 cm−1. Systematic study of the hyperfine structure (HFS) of the a3Σ+ state for levels with va∈0,27 and Na∈24,90 shows that the splitting monotonically increases with va. The spectroscopic study was supported by ab initio calculations of the magnetic hyperfine interaction in X1Σ+ and a3Σ+ states. The discovered variation of the electronic matrix elements with the internuclear distance R is in a good agreement with the observed va-dependencies of the HFS. Overall set of available experimental data on the a3Σ+ state was used to improve the potential energy curve particularly near a bottom, providing the refined dissociation energy De=267.21(1) cm−1. The ab initio HFS matrix elements, combined with the empirical X1Σ+ and a3Σ+ PECs in the framework of the invented coupled-channel deperturbation model, reproduce the experimental term values of both ground states within 0.003 cm−1 accuracy up to their common dissociation limit.
Abstract Background Although the mortality for gastric cancer is decreasing in Western Europe and United States, it still remains high in Eastern Europe. This study was aimed at evaluating short- and ...long-term results of surgical treatment of gastric cancer performed in Latvia Oncology Center. Methods Retrospectively collected data from 461 patients who underwent gastrectomy with curative intent in Latvia Oncology Center from January 2001 to December 2005 were analyzed statistically. Results An average (range) of 92.2 (81–102) R0–R1 gastrectomies was performed each year. Post-operative complications occurred in 75 patients (16.3%); in-hospital mortality was 3.3%. The overall 5-year survival was 50.8%. In 444 cases (96.3%) there was histopathologic confirmation of R0-resection with a 5-year survival of 52.5% ( P < 0.001). Considering pT category, 5-year survival was 88.6% for pT1 patients, 65% for pT2, 42.3% for pT3 and 27% for pT4 ( P < 0.001). Considering pN category, 5-year survival was 67% for pN0 patients, 30% for pN1 and 29% for pN2-3 ( P < 0.001). Conclusions Clinico-pathologic characteristics of patients who underwent resection with curative intent are comparable to other Western experiences. Short- as well as long-term results are also similar if not for pN+ patients where no difference between pN1 and pN2 cases was observed.
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