Atomic clocks are vital in a wide array of technologies and experiments, including tests of fundamental physics
. Clocks operating at optical frequencies have now demonstrated fractional stability ...and reproducibility at the 10
level, two orders of magnitude beyond their microwave predecessors
. Frequency ratio measurements between optical clocks are the basis for many of the applications that take advantage of this remarkable precision. However, the highest reported accuracy for frequency ratio measurements has remained largely unchanged for more than a decade
. Here we operate a network of optical clocks based on
Al
(ref.
),
Sr (ref.
) and
Yb (ref.
), and measure their frequency ratios with fractional uncertainties at or below 8 × 10
. Exploiting this precision, we derive improved constraints on the potential coupling of ultralight bosonic dark matter to standard model fields
. Our optical clock network utilizes not just optical fibre
, but also a 1.5-kilometre free-space link
. This advance in frequency ratio measurements lays the groundwork for future networks of mobile, airborne and remote optical clocks that will be used to test physical laws
, perform relativistic geodesy
and substantially improve international timekeeping
.
A one-pot, bottom-up assembly of a pyrimidine-containing porous-organic polymer (PyPOP) was conducted to homogenously deposit the PyPOP atop unmodified graphene sheets, affording a composite material ...PyPOP@G. The PyPOP demonstrated an appreciable affinity toward CO2 capture but was found to be largely insulating, hindering its usage in potential electrochemical conversion of CO2. However, its composite with graphene was found to be microporous, with maintained affinity toward CO2 and furthermore demonstrated significant electrochemical activity toward CO2 reduction (5 mA cm-2 at -1.6 V), not observed in either of its two components separately.
Herein, we report a facile approach towards the construction of poly-functional porous organic polymers (POPs). The functional groups employed were selected to span the range of Lewis-base to neutral ...to Lewis-acid character. Our results underline the effect of chemical functionality on the observed Qst for CO2 adsorption inside the material, being largest for functional groups with electron donating O- and N-centered Lewis base sites. Our systematic investigation within a family of POPs revealed a wide range for CO2 heat of adsorption (23.8-53.8 kJ mol-1) that is clearly associated with the chemical nature of the functional groups present. In addition, post-synthetic modification of POPs reported herein demonstrated a facile pathway to dramatically enhance carbon dioxide uptake energetics.
To explore the impact of using topical stem cell-conditioned medium (SC-CM) after fractional carbon dioxide laser (FCL) vs. combined FCL and platelet-rich plasma (PRP) or FCL alone in treatment of ...atrophic acne scars.
Thirty-three patients were randomly divided into two split-face groups. Group I (n = 17) received FCL plus topical SC-CM on one side or FCL plus saline on the other. Group II (n = 16) received FCL plus topical PRP or SC-CM. All patients had three monthly sessions. Clinical assessment was done at each visit, with a final assessment after 3 months. Skin biopsies were obtained for histological and quantitative molecular analysis after treatment.
No significant difference in clinical improvement of acne scars was observed between the FCL/SC-CM and FCL only sides (p = .63), while better and faster improvement was detected on FCL/PRP side compared to FCL/SC-CM side (p = .006). There was no significant difference in downtime or adverse effects between the treated sides in either group. Dermal collagen was increased and procollagen type I gene was upregulated in both FCL/PRP and FCL/SC-CM sides compared to FCL only sides (p = .001 and p = .041, respectively).
Topical SC-CM could potentially enhance the efficacy of FCL. However, PRP seems to be a better alternative.
Comparisons of high-accuracy optical atomic clocks1 are essential for precision tests of fundamental physics2, relativistic geodesy3–5 and the anticipated redefinition of the second by the ...International System of Units6. The scientific reach of these applications is restricted by the statistical precision of comparison measurements between clocks realized with different atomic species. The instability of individual clocks is limited by the finite coherence time of the optical local oscillator, which bounds the maximum atomic interrogation time. Here we experimentally demonstrate differential spectroscopy7, a comparison protocol that enables interrogating times beyond the optical local oscillator coherence time. By phase coherently linking a zero-dead-time8 Yb optical lattice clock with an Al+ single-ion clock via an optical frequency comb and performing synchronized Ramsey spectroscopy, we show an improvement in comparison instability relative to previous results9 of nearly an order of magnitude. This result represents one of the most stable interspecies clock comparisons to date.Interspecies comparisons between atomic optical clocks are important for several technological applications. A recently proposed spectroscopy technique extends the interrogation times of clocks, leading to highly stable comparison between species.
We report on utilization of 1D and 2D 13C cross-polarization magic angle spinning (CPMAS) and MAS solid-state NMR spectroscopy in probing the binding sites and dynamical processes of 13C-enriched CO2 ...inside the pores of a pyridine-containing porous organic polymer (POP). Our findings from the spectroscopic measurements conducted on the evacuated sample and on the sample dosed with 800 mbar 13CO2 indicated preferential adsorption of the CO2 molecules at the vicinity of the basic binding sites within the POP, the pyridine rings. We further demonstrate the results of a computational study for probing the most favorable binding sites of CO2 inside a geometrically optimized model of the polymer in an attempt to better rationalize the experimental findings from 13C solid-state NMR investigations. Because of the amorphous nature of the studied POP, also being observed for a large number of emerging microporous solids, this combined approach can prove useful and versatile toward drawing a detailed picture of the gas–solid interactions, aiming for enhanced designs for futuristic materials toward CO2 capture and sequestration.
A number of permanently porous polymers containing Ru(bpy) n photosensitizer or a cobaloxime complex, as a proton-reduction catalyst, were constructed via one-pot Sonogashira–Hagihara (SH) ...cross-coupling reactions. This process required minimal workup to access porous platforms with control over the apparent surface area, pore volume, and chemical functionality from suitable molecular building blocks (MBBs) containing the Ru or Co complexes, as rigid and multitopic nodes. The cobaloxime molecular building block, generated through in situ metalation, afforded a microporous solid that demonstrated noticeable catalytic activity toward hydrogen-evolution reaction (HER) with remarkable recyclability. We further demonstrated, in two cases, the ability to affect the excited-state lifetime of the covalently immobilized Ru(bpy)3 complex attained through deliberate utilization of the organic linkers of variable dimensions. Overall, this approach facilitates construction of tunable porous solids, with hybrid composition and pronounced chemical and physical stability, based on the well-known Ru(bpy) n or the cobaloxime complexes.
Melanoma, a highly invasive type of skin cancer that penetrates the entire dermis layer, is associated with increased mortality rates. Excessive exposure of the skin to sunlight, specifically ...ultraviolet radiation, is the underlying cause of this malignant condition. The appearance of unique skin moles represents a visible clue, referred to as the “ugly duckling” sign, indicating the presence of melanoma and its association with cellular DNA damage. This research aims to explore potential biomarkers derived from microarray data, employing bioinformatics techniques and methodologies, for a thorough investigation of melanoma skin cancer. The microarray dataset for melanoma skin cancer was obtained from the GEO database, and thorough data analysis and quality control measures were performed to identify differentially expressed genes (DEGs). The top 14 highly expressed DEGs were identified, and their gene information and protein sequences were retrieved from the NCBI gene and protein database. These proteins were further analyzed for domain identification and network analysis. Gene expression analysis was conducted to visualize the upregulated and downregulated genes. Additionally, gene metabolite network analysis was carried out to understand the interactions between highly interconnected genes and regulatory transcripts. Molecular docking was employed to investigate the ligand-binding sites and visualize the three-dimensional structure of proteins. Our research unveiled a collection of genes with varying expression levels, some elevated and others reduced, which could function as promising biomarkers closely linked to the development and advancement of melanoma skin cancer. Through molecular docking analysis of the GINS2 protein, we identified two natural compounds (PubChem-156021169 and PubChem-60700) with potential as inhibitors against melanoma. This research has implications for early detection, treatment, and understanding the molecular basis of melanoma.
Optical atomic clocks are poised to redefine the Système International (SI) second, thanks to stability and accuracy more than 100 times better than the current microwave atomic clock standard. ...However, the best optical clocks have not seen their performance transferred to the electronic domain, where radar, navigation, communications, and fundamental research rely on less stable microwave sources. By comparing two independent optical-to-electronic signal generators, we demonstrate a 10-gigahertz microwave signal with phase that exactly tracks that of the optical clock phase from which it is derived, yielding an absolute fractional frequency instability of 1 × 10
in the electronic domain. Such faithful reproduction of the optical clock phase expands the opportunities for optical clocks both technologically and scientifically for time dissemination, navigation, and long-baseline interferometric imaging.
A one-pot, bottom-up assembly of a pyrimidine-containing porous-organic polymer (PyPOP) was conducted to homogenously deposit the PyPOP atop unmodified graphene sheets, affording a composite material ...PyPOP@G. The PyPOP demonstrated an appreciable affinity toward CO
capture but was found to be largely insulating, hindering its usage in potential electrochemical conversion of CO
. However, its composite with graphene was found to be microporous, with maintained affinity toward CO
and furthermore demonstrated significant electrochemical activity toward CO
reduction (5 mA cm
at -1.6 V), not observed in either of its two components separately.
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