Precision spectroscopy of atomic systems
is an invaluable tool for the study of fundamental interactions and symmetries
. Recently, highly charged ions have been proposed to enable sensitive tests of ...physics beyond the standard model
and the realization of high-accuracy atomic clocks
, owing to their high sensitivity to fundamental physics and insensitivity to external perturbations, which result from the high binding energies of their outer electrons. However, the implementation of these ideas has been hindered by the low spectroscopic accuracies (of the order of parts per million) achieved so far
. Here we cool trapped, highly charged argon ions to the lowest temperature reported so far, and study them using coherent laser spectroscopy, achieving an increase in precision of eight orders of magnitude. We use quantum logic spectroscopy
to probe the forbidden optical transition in
Ar
at a wavelength of 441 nanometres and measure its excited-state lifetime and g-factor. Our work unlocks the potential of highly charged ions as ubiquitous atomic systems for use in quantum information processing, as frequency standards and in highly sensitive tests of fundamental physics, such as searches for dark-matter candidates
or violations of fundamental symmetries
.
Understanding chemical transformations of contaminants and the resulting products is extremely important in devising proper monitoring methods for such contaminants and in assessing potential human ...exposure to the transformation products in the environment. Ultraviolet (UV) light from the sun can induce various photochemical transformations of contaminants in the environment. Alkylnaphthalenes are light-molecular-weight polycyclic aromatic hydrocarbons (PAHs) which are one of the most widespread organic pollutants present in ambient air as a result of a variety of in-complete combustion sources. In this study, 1-methylnapthalene,a typical example of an alkylnaphthalene, was subjected to UV irradiation to investigate its transformation in the presence and absence of air. Twenty-one products were detected in the reaction mixtures. Some photo-oxidation products were identified, including both ring-opened and ring-retained oxygenated compounds, such as 1-naphthaldehyde, 1-naphthoic acid, 1-naphthalenemethanol and phthalic anhydride. Although dimeric products were observed in the presence of air, more were found in the presence of helium or argon gas, indicating a different photo-oxidation pathway from those commonly observed in other media, such as water. Under just 48 hours of exposure to the UV light in the presence of air, three major products were formed with a production yield of about 10% each. Compared to 1-methylnapthalene, the UV induced transformation products observed in this study are more volatile, acidic, water soluble or toxic. The formation of these products may significantly change our understanding of the risks assessed solely from the parent compound in contaminants research and supports the inclusion of airborne transformations of the parent compound in risk assessment.
Objective
To histologically assess the hard and soft tissue changes after insertion of cleaned and activated titanium implants using plasma of argon.
Materials and methods
Eight dogs were included in ...this study. The mandibular premolars and first molars were extracted. For each hemi‐mandible, four implants, 7 mm long and 3.3 mm of diameter, with a ZirTi surface were used. The surface of two implants was randomly treated with argon plasma (test), while the other two implants were left untreated (control). After 1 month, the same procedure was performed in the contralateral hemi‐mandible. The amount of old bone, new bone, overall value of old bone plus new bone, and soft tissue was histologically evaluated.
Results
After 1 month of healing, high percentages of new bone in close contact with the implant surface were found at both the treated (60.1% ± 15.6%; 95% CI 56.5%–78.0%) and untreated (57.2% ± 13.1%; 95% CI 49.3%–67.5%) implants. Low percentages of old bone were found at this stage of healing, at both the treated (4.4% ± 3.0%; 95% CI 1.2%–5.4%) and untreated (3.4% ± 3.1%; 95% CI 0.6%–4.9%) implants. Not statistically significant differences were found between groups (p > .05). After 2 months of healing, treated implants presented a significantly higher (p = .012) new bone formation (72.5% ± 12.4%; 95% CI 69.6%–86.8%) compared to untreated sites (64.7% ± 17.3%; 95% CI 59.4%–83.3%). Controversially, no difference (p = .270) in terms of old bone was present between treated (3.1% ± 1.7%, 95% CI 1.8%–4.2%) and untreated implants (3.8% ± 1.9%, 95% CI 3.2%–5.8%). Significant differences (p = .018) in terms of total mineralized bone were found between treated (75.6% ± 13.0%, 95% CI 73.3%–91.3%) and untreated implants (68.4% ± 16.8%; 95% CI 64.2%–87.6%).
Conclusions
Implants treated using plasma of argon was demonstrated to reach a higher bone‐to‐implant contact when compared to untreated implants.
Whilst there has been progress in supportive treatment for traumatic brain injury (TBI), specific neuroprotective interventions are lacking. Models of ischaemic heart and brain injury show the ...therapeutic potential of argon gas, but it is still not known whether inhaled argon (iAr) is protective in TBI. We tested the effects of acute administration of iAr on brain oedema, tissue micro-environmental changes, neurological functions, and structural outcome in a mouse model of TBI.
Anaesthetised adult C57BL/6J mice were subjected to severe TBI by controlled cortical impact. Ten minutes after TBI, the mice were randomised to 24 h treatments with iAr 70%/O2 30% or air (iCtr). Sensorimotor deficits were evaluated up to 6 weeks post-TBI by three independent tests. Cognitive function was evaluated by Barnes maze test at 4 weeks. MRI was done to examine brain oedema at 3 days and white matter damage at 5 weeks. Microglia/macrophages activation and functional commitment were evaluated at 1 week after TBI by immunohistochemistry.
iAr significantly accelerated sensorimotor recovery and improved cognitive deficits 1 month after TBI, with less white matter damage in the ipsilateral fimbria and body of the corpus callosum. Early changes underpinning protection included a reduction of pericontusional vasogenic oedema and of the inflammatory response. iAr significantly reduced microglial activation with increases in ramified cells and the M2-like marker YM1.
iAr accelerates recovery of sensorimotor function and improves cognitive and structural outcome 1 month after severe TBI in adult mice. Early effects include a reduction of brain oedema and neuroinflammation in the contused tissue.
Different applications require different customizations of silicon photomultiplier (SiPM) technology. We present a review on the latest SiPM technologies developed at Fondazione Bruno Kessler (FBK, ...Trento), characterized by a peak detection efficiency in the near-UV and customized according to the needs of different applications. Original near-UV sensitive, high-density SiPMs (NUV-HD), optimized for Positron Emission Tomography (PET) application, feature peak photon detection efficiency (PDE) of 63% at 420 nm with a 35 um cell size and a dark count rate (DCR) of 100 kHz/mm². Correlated noise probability is around 25% at a PDE of 50% at 420 nm. It provides a coincidence resolving time (CRT) of 100 ps FWHM (full width at half maximum) in the detection of 511 keV photons, when used for the readout of LYSO(Ce) scintillator (Cerium-doped lutetium-yttrium oxyorthosilicate) and down to 75 ps FWHM with LSO(Ce:Ca) scintillator (Cerium and Calcium-doped lutetium oxyorthosilicate). Starting from this technology, we developed three variants, optimized according to different sets of specifications. NUV-HD⁻LowCT features a 60% reduction of direct crosstalk probability, for applications such as Cherenkov telescope array (CTA). NUV-HD⁻Cryo was optimized for cryogenic operation and for large photosensitive areas. The reference application, in this case, is the readout of liquid, noble-gases scintillators, such as liquid Argon. Measurements at 77 K showed a remarkably low value of the DCR of a few mHz/mm². Finally, vacuum-UV (VUV)-HD features an increased sensitivity to VUV light, aiming at direct detection of photons below 200 nm. PDE in excess of 20% at 175 nm was measured in liquid Xenon. In the paper, we discuss the specifications on the SiPM related to different types of applications, the SiPM design challenges and process optimizations, and the results from the experimental characterization of the different, NUV-sensitive technologies developed at FBK.
Stress shielding and osseointegration are two main challenges in bone regeneration, which have been targeted successfully by chemical and physical surface modification methods. Direct irradiation ...synthesis (DIS) is an energetic ion irradiation method that generates self-organized nanopatterns conformal to the surface of materials with complex geometries (e.g., pores on a material surface). This work exposes porous titanium samples to energetic argon ions generating nanopatterning between and inside pores. The unique porous architected titanium (Ti) structure is achieved by mixing Ti powder with given amounts of spacer NaCl particles (vol % equal to 30%, 40%, 50%, 60%, and 70%), compacted and sintered, and combined with DIS to generate a porous Ti with bone-like mechanical properties and hierarchical topography to enhance Ti osseointegration. The porosity percentages range between 25% and 30% using 30 vol % NaCl space-holder (SH) volume percentages to porosity rates of 63%-68% with SH volume of 70 vol % NaCl. Stable and reproducible nanopatterning on the flat surface between pores, inside pits, and along the internal pore walls are achieved, for the first time on any porous biomaterial. Nanoscale features were observed in the form of nanowalls and nanopeaks of lengths between 100 and 500 nm, thicknesses of 35-nm and heights between 100 and 200 nm on average. Bulk mechanical properties that mimic bone-like structures were observed along with increased wettability (by reducing contact values). Nano features were cell biocompatible and enhanced in vitro pre-osteoblast differentiation and mineralization. Higher alkaline phosphatase levels and increased calcium deposits were observed on irradiated 50 vol % NaCl samples at 7 and 14 days. After 24 h, nanopatterned porous samples decreased the number of attached macrophages and the formation of foreign body giant cells, confirming nanoscale tunability of M1-M2 immuno-activation with enhanced osseointegration.
The 40Ar/39Ar dating technique is a high precision (<0.1%) method with wide application to geological samples. However, the method is predicated on the availability of natural mineral standards of ...known age. Widely used 40Ar/39Ar standards include sanidine from the (ca. 28Ma) Fish Canyon Tuff (FCT) and the (ca. 1.2Ma) Alder Creek Rhyolite (ACR). Despite common usage, the ages of FCT and ACR sanidine have proven contentious, with reported values varying by >2%; well outside the ±0.1% aspiration of EARTHTIME (www.earth-time.org). The current study presents ultra-high precision, multi-collector 40Ar/39Ar results for FCT and ACR sanidine, using a new generation ARGUSVI mass spectrometer. These analyses demonstrate the significantly higher (by a factor of ∼10) level of precision achievable using the ARGUSVI system, compared to most previous studies. Significantly, 40Ar/39Ar step-heating analyses resolve distinct age gradients for both FCT and ACR sanidine. Possible explanations for these gradients include combinations of recoil loss of 39Ar, instrumental bias, isotopic fractionation during step-heating, thermally induced argon loss and/or extraneous argon contamination. Minor recoil loss of 39Ar and partial retention of inherited argon during extended magma residence, are deemed the most plausible causes of the age discordance. Given this assumption, we calculate revised (maximum?) eruption ages of 28.01±0.04Ma (2σ) for FCT and 1.178±0.002Ma (2σ) for ACR, relative to the astronomically calibrated age of A1 Tephra sanidine, Crete Rivera et al. (2011)Earth Planet Sci. Lett.311, 420–426. Nonetheless, the ARGUSVI data demonstrate that FCT and ACR sanidine are non-ideal as high precision 40Ar/39Ar standards, with different heating protocols likely to induce inter-laboratory bias. The current findings account for at least some of the scatter in inter-calibration ages reported previously for various 40Ar/39Ar standards. In broader terms, the results mandate a re-evaluation of the astronomically calibrated ages for these and other sanidine samples, while the new generation of multi-collector mass spectrometers provides the means to further evaluate 40Ar/39Ar ages used to define new decay constants and standard ages.
Pelvic radiation is a commonly utilized treatment for malignancy of the genitourinary and lower gastrointestinal tract. Radiation proctitis and the resultant clinical picture varies from asymptomatic ...to potentially life threatening. Similarly, treatment options also vary greatly, from medical therapy to surgical intervention. Commonly utilized medical therapy includes sucralfate enemas, antibiotics, 5-aminosalicylic acid derivatives, probiotics, antioxidants, short-chain fatty acids, formalin instillation and fractionated hyperbaric oxygen. More invasive treatments include endoscopic-based, focally ablative interventions such as dilation, heater and bipolar cautery, neodymium/yttrium aluminum garnet argon laser, radiofrequency ablation or argon plasma coagulation. Despite its relatively common frequency, there is a dearth of existing literature reporting headto-head comparisons of the various treatment options via a randomized controlled approach. The purpose of our review was to present the reader a consolidation of the existing evidence-based literature with the goal of highlighting the comparative effectiveness and risks of the various treatment approaches. Finally, we outline a pragmatic approach to the treatment of radiation proctitis. In light of the lack of randomized data, our goal is to pursue as least invasive an approach as possible, with escalation of care tailored to the severity of the patient’s symptoms. For those cases that are clinicallyasymptomatic or only mildly symptomatic, observation or medical management can be considered. Once a patient fails such management or symptoms become more severe, invasive procedures such as endoscopically based focal ablation or surgical intervention can be considered. Although not all recommendations are supported by level I evidence, reported case series and single-institutional studies in the literature suggest that successful treatment with cessation of symptoms can be obtained in the majority of cases.
Metallurgical converters such as the argon–oxygen decarburization (AOD) converter generally utilize gas blowing for the mixing and refinement of liquid steel. Due to the harsh environment of the ...complex and opaque system, it is common practice to study the stirring of the process through physical and numerical models. Effective mixing in the bath has an important role in refinement such as decarburization and has been vividly studied before. However, high‐temperature chemical reactions that also play a major role are sparsely investigated. With the help of modeling, a computational fluid dynamics model coupled with chemical reactions is developed, allowing the study of both dynamic fluid transport and chemical reactions. Herein, the chemical reactions for a single gas bubble in the AOD are investigated. The study shows that a 60 mm oxygen gas bubble rapidly reacts with the melt and is saturated with carbon in 0.2–0.25 s at low‐pressure levels. The saturation time is affected by the pressure and the composition of the injected gas bubble. The impact of ferrostatic pressure on the reactions is more significant at larger depth differences.
A coupled thermodynamic and fluid transport model on a dynamic bubble in liquid steel is developed to fundamentally investigate pressure differences in decarburization reactions. The impact of ferrostatic pressure is more significant at larger depth differences. A bubble closer to the surface is saturated at higher carbon levels due to the lowered partial pressure of the elements in the gas.
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