170 research outputs found
Dichroic atomic vapor laser lock with multi-gigahertz stabilization range
A dichroic atomic vapor laser lock (DAVLL) system exploiting
buffer-gas-filled millimeter-scale vapor cells is presented. This system offers
similar stability as achievable with conventional DAVLL system using bulk vapor
cells, but has several important advantages. In addition to its compactness, it
may provide continuous stabilization in a multi-gigahertz range around the
optical transition. This range may be controlled either by changing the
temperature of the vapor or by application of a buffer gas under an appropriate
pressure. In particular, we experimentally demonstrate the ability of the
system to lock the laser frequency between two hyperfine components of the
Rb ground state or as far as 16 GHz away from the closest optical
transition.Comment: 11 pages, 7 figures. Published in Review of Scientific Instruments
201
Investigation of microwave transitions and nonlinear magneto-optical rotation in anti-relaxation-coated cells
Using laser optical pumping, widths and frequency shifts are determined for
microwave transitions between ground-state hyperfine components of Rb
and Rb atoms contained in vapor cells with alkane anti-relaxation
coatings. The results are compared with data on Zeeman relaxation obtained in
nonlinear magneto-optical rotation (NMOR) experiments, a comparison important
for quantitative understanding of spin-relaxation mechanisms in coated cells.
By comparing cells manufactured over a forty-year period we demonstrate the
long-term stability of coated cells, an important property for atomic clocks
and magnetometers
The New Sensing Fibre for Application in Optical Fibre Current Sensor
The present paper deals with investigations concerning optical fibre current sensors. They are mainly applied in measurements of the intensity of the electric current in the power lines as so-called optical transformers of the electrical current. The most important advantages of fibre current sensors are: safety of service, insulating power as well as their insensitiveness to electromagnetic interference. The investigations were concentrated on designing of adequate sensing fibre, and particularly on the choice of an adequate kind of glass, of which this fibre could be made. Besides, also the head of the fibre current sensor was designed, basing on the suggested and produced sensing fibre. The paper presents the results of magneto-optic tests of the glass and the sensing fibre
Characterization of the global network of optical magnetometers to search for exotic physics (GNOME)
The Global Network of Optical Magnetometers to search for Exotic physics (GNOME) is a network of geographically separated, time-synchronized, optically pumped atomic magnetometers that is being used to search for correlated transient signals heralding exotic physics. The GNOME is sensitive to nuclear- and electron-spin couplings to exotic fields from astrophysical sources such as compact dark-matter objects (for example, axion stars and domain walls). Properties of the GNOME sensors such as sensitivity, bandwidth, and noise characteristics are studied in the present work, and features of the network’s operation (e.g., data acquisition, format, storage, and diagnostics) are described. Characterization of the GNOME is a key prerequisite to searches for and identification of exotic physics signatures
Structural basis for native agonist and synthetic inhibitor recognition by the Pseudomonas aeruginosa quorum sensing regulator PqsR (MvfR)
Bacterial populations co-ordinate gene expression collectively through quorum sensing (QS), a cell-to-cell communication mechanism employing diffusible signal molecules. The LysR-type transcriptional regulator (LTTR) protein PqsR (MvfR) is a key component of alkyl-quinolone (AQ)-dependent QS in Pseudomonas aeruginosa. PqsR is activated by 2-alkyl-4-quinolones including the Pseudomonas quinolone signal (PQS; 2-heptyl-3-hydroxy-4(1H)-quinolone), its precursor 2-heptyl-4- hydroxyquinoline (HHQ) and their C9 congeners, 2-nonyl-3-hydroxy-4(1H)-quinolone (C9-PQS) and 2-nonyl-4-hydroxyquinoline (NHQ). These drive the autoinduction of AQ biosynthesis and the up-regulation of key virulence determinants as a function of bacterial population density. Consequently, PqsR constitutes a potential target for novel antibacterial agents which attenuate infection through the blockade of virulence. Here we present the crystal structures of the PqsR co-inducer binding domain (CBD) and a complex with the native agonist NHQ. We show that the structure of the PqsR CBD has an unusually large ligand-binding pocket in which a native AQ agonist is stabilized entirely by hydrophobic interactions. Through a ligand-based design strategy we synthesized and evaluated a series of 50 AQ and novel quinazolinone (QZN) analogues and measured the impact on AQ biosynthesis, virulence gene expression and biofilm development. The simple exchange of two isosteres (OH for NH2) switches a QZN agonist to an antagonist with a concomitant impact on the induction of bacterial virulence factor production. We also determined the complex crystal structure of a QZN antagonist bound to PqsR revealing a similar orientation in the ligand binding pocket to the native agonist NHQ. This structure represents the first description of an LTTR-antagonist complex. Overall these studies present novel insights into LTTR ligand binding and ligand-based drug design and provide a chemical scaffold for further anti-P. aeruginosa virulence drug development by targeting the AQ receptor PqsR
Controlling atomic vapor density in paraffin-coated cells using light-induced atomic desorption
Atomic-vapor density change due to light induced atomic desorption (LIAD) is
studied in paraffin-coated rubidium, cesium, sodium and potassium cells. In the
present experiment, low-intensity probe light is used to obtain an absorption
spectrum and measure the vapor density, while light from an argon-ion laser,
array of light emitting diodes, or discharge lamp is used for desorption.
Potassium is found to exhibit significantly weaker LIAD from paraffin compared
to Rb and Cs, and we were unable to observe LIAD with sodium. A simple LIAD
model is applied to describe the observed vapor-density dynamics, and the role
of the cell's stem is explored through the use of cells with lockable stems.
Stabilization of Cs vapor density above its equilibrium value over 25 minutes
is demonstrated. The results of this work could be used to assess the use of
LIAD for vapor-density control in magnetometers, clocks, and gyroscopes
utilizing coated cells.Comment: 10 pages, 11 figure
The cystic fibrosis microbiome in an ecological perspective and its impact in antibiotic therapy
The recent focus on the cystic fibrosis (CF) complex microbiome has led to the recognition that the microbes can interact between them and with the host immune system, affecting the disease progression and treatment routes. Although the main focus remains on the interactions between traditional pathogens, growing evidence supports the contribution and the role of emergent species. Understanding the mechanisms and the biological effects involved in polymicrobial interactions may be the key to improve effective therapies and also to define new strategies for disease control. This review focuses on the interactions between microbe-microbe and host-microbe, from an ecological point of view, discussing their impact on CF disease progression. There are increasing indications that these interactions impact the success of antimicrobial therapy. Consequently, a new approach where therapy is personalized to patients by taking into account their individual CF microbiome is suggested.Portuguese Foundation for Science and Technology (FCT), the strategic funding of UID/BIO/04469/2013-CEB and UID/EQU/00511/2013-LEPABE units. This study was also supported by FCT and the European Community fund FEDER, through Program COMPETE, under the scope of the Projects “DNA mimics” PIC/IC/82815/2007, RECI/BBB-EBI/0179/2012 (FCOMP-01-0124-FEDER-027462), “BioHealth—Biotechnology and Bioengineering approaches to improve health quality”, Ref. NORTE-07-0124-FEDER-000027 and NORTE-07-0124-FEDER-000025—RL2_ Environment and Health, co-funded by the Programa Operacional Regional do Norte (ON.2 – O Novo Norte), QREN, FEDER. The authors also acknowledge the grant of Susana P. Lopes (SFRH/BPD/95616/2013) and of the COST-Action TD1004: Theragnostics for imaging and therapy
Characterization of the global network of optical magnetometers to search for exotic physics (GNOME)
The Global Network of Optical Magnetometers to search for Exotic physics (GNOME) is a network of geographically separated, time-synchronized, optically pumped atomic magnetometers that is being used to search for correlated transient signals heralding exotic physics. The GNOME is sensitive to nuclear- and electron-spin couplings to exotic fields from astrophysical sources such as compact dark-matter objects (for example, axion stars and domain walls). Properties of the GNOME sensors such as sensitivity, bandwidth, and noise characteristics are studied in the present work, and features of the network’s operation (e.g., data acquisition, format, storage, and diagnostics) are described. Characterization of the GNOME is a key prerequisite to searches for and identification of exotic physics signatures
Gamma Factory at CERN – novel research tools made of light
We discuss the possibility of creating novel research tools by producing and
storing highly relativistic beams of highly ionised atoms in the CERN
accelerator complex, and by exciting their atomic degrees of freedom with
lasers to produce high-energy photon beams. Intensity of such photon beams
would be by several orders of magnitude higher than offered by the presently
operating light sources, in the particularly interesting gamma-ray energy
domain of 0.1-400 MeV. In this energy range, the high-intensity photon beams
can be used to produce secondary beams of polarised electrons, polarised
positrons, polarised muons, neutrinos, neutrons and radioactive ions. New
research opportunities in a wide domain of fundamental and applied physics can
be opened by the Gamma Factory scientific programme based on the above primary
and secondary beams.Comment: 12 pages; presented by W. Placzek at the XXV Cracow Epiphany
Conference on Advances in Heavy Ion Physics, 8-11 January 2019, Cracow,
Polan
- …