A grating-chip atomic fountain

Cold atom fountain clocks provide exceptional long term stability as they increase interrogation time at the expense of a larger size. We present a compact cold atom fountain using a grating magneto-optical trap (GMOT) to laser cool and launch the atoms in a simplified optical setup. The fountain is evaluated using coherent population trapping and demonstrates improved single-shot stability from the launch. Ramsey times up to 100ms were measured with a corresponding fringe linewidth of 5Hz. This technique could improve both short and long-term stability of cold atom clocks while remaining compact for portable applications

Antibacterial Activity of Partially Oxidized Ag/Au Nanoparticles against the Oral Pathogen Porphyromonas gingivalis

Advances in nanotechnology provide opportunities for the prevention and treatment of periodontal disease. While physicochemical properties of Ag containing nanoparticles (NPs) are known to influence the magnitude of their toxicity, it is thought that nanosilver can be made less toxic to eukaryotes by passivation of the NPs with a benign metal. Moreover, the addition of other noble metals to silver nanoparticles, in the alloy formulation, is known to alter the silver dissolution behavior. Thus, we synthesized glutathione capped Ag/Au alloy bimetallic nanoparticles (NPs) via the galvanic replacement reaction between maltose coated Ag NPs and chloroauric acid (HAuCl4) in 5% aqueous triblock F127 copolymer solution. We then compared the antibacterial activity of the Ag/Au NPs to pure Ag NPs on Porphyromonas gingivalis W83, a key pathogen in the development of periodontal disease. Only partially oxidized glutathione capped Ag and Ag/Au (Au : Ag ≈ 0.2) NPs inhibited the planktonic growth of P. gingivalis W83. This effect was enhanced in the presence of hydrogen peroxide, which simulates the oxidative stress environment in the periodontal pocket during chronic inflammation

Towards a compact atomic clock based on coherent population trapping and the grating magneto-optical trap

The combination of coherent population trapping (CPT) and laser cooled atoms is a promising platform for realizing the next generation of compact atomic frequency references. Towards this goal, we have developed an apparatus based on the grating magneto-optical trap (GMOT) and the high-contrast lin ⊥ lin CPT scheme in order to explore the performance that can be achieved. One important trade-off for cold-atom systems arises from the need to simultaneously maximize the number of cold atoms available for interrogation and the repetition rate of the system. This compromise can be mitigated by recapturing cold atoms from cycle to cycle. Here, we report a quantitative characterization of the cold atom number in the recapture regime for our system, which will enable us to optimize this trade-off. We also report recent measurements of the short-term frequency stability with a short-term Allan deviation of 3 × 10-11/τ up to an averaging time of τ = 10 s

Cold-atom clock based on a diffractive optic

Clocks based on cold atoms offer unbeatable accuracy and long-term stability, but their use in portable quantum technologies is hampered by a large physical footprint. Here, we use the compact optical layout of a grating magneto-optical trap (gMOT) for a precise frequency reference. The gMOT collects 10 7 87Rb atoms, which are subsequently cooled to 20 µK in optical molasses. We optically probe the microwave atomic ground-state splitting using lin┴lin polarised coherent population trapping and a Raman-Ramsey sequence. With ballistic drop distances of only 0.5 mm, the measured short-term fractional frequency stability is 2 × 10 −11/√τ

Towards a compact, optically-interrogated, cold-atom microwave clock

A compact platform for cold atoms opens a range of exciting possibilities for portable, robust, and accessible quantum sensors. In this work we report on the development of a cold-atom microwave clock in a small package. Our work utilises the grating magneto-optical trap and high-contrast coherent population trapping in the lin⊥lin polarisation scheme. We optically probe the atomic round-state splitting of cold 87Rb atoms using a Ramsey-like sequence whilst the atoms are in free-fall. We have measured a short-term fractional frequency stability of 5×10−11/√t with a projected quantum projection noise limit at the 10 −13/√t level

Impact of laser frequency noise in coherent population trapping with cold atoms

Laser-cooled atoms and coherent population trapping (CPT) are promising tools for realizing a compact microwave frequency reference with excellent stability. To realize a high performance device, it is necessary to understand and minimize all sources of technical noise. Here, we investigate the role of laser frequency noise in cold-atom CPT with an apparatus based on the grating magneto-optical trap (GMOT). We compare the performance of our setup with an external cavity diode laser (ECDL) and a distributed feedback diode laser (DFB). With the DFB, laser frequency noise is one of the dominant noise sources in our system. With the ECDL, it is significantly reduced. We also report frequency stability measurements of our apparatus with a short-term Allan deviation Sigma_y (tau) ≈ 3(times)10-11/rt τ up to τ= 10 s

Pharmacological Assessment of the Medicinal Potential of Acacia mearnsii De Wild.: Antimicrobial and Toxicity Activities

Acacia mearnsii De Wild. (Fabaceae) is a medicinal plant used in the treatment of microbial infections in South Africa without scientific validation of its bioactivity and toxicity. The antimicrobial activity of the crude acetone extract was evaluated by both agar diffusion and macrobroth dilution methods while its cytotoxicity effect was assessed with brine shrimp lethality assay. The study showed that both bacterial and fungal isolates were highly inhibited by the crude extract. The MIC values for the gram-positive bacteria (78.1–312.5) μg/mL, gram-negative bacteria (39.1–625) μg/mL and fungal isolates (625–5000) μg/mL differ significantly. The bacteria were more susceptible than the fungal strains tested. The antibiosis determination showed that the extract was more (75%) bactericidal than bacteriostatic (25%) and more fungicidal (66.67%) than fungistatic (33.33%). The cytotoxic activity of the extract was observed between 31.25 μg/mL and 500 μg/mL and the LC50 value (112.36 μg/mL) indicates that the extract was nontoxic in the brine shrimp lethality assay (LC50 > 100 μg/mL). These results support the use of A. mearnsii in traditional medicine for treatment of microbial infections. The extract exhibiting significant broad spectrum antimicrobial activity and nontoxic effects has potential to yield active antimicrobial compounds

Patient Disclosure about Herb and Supplement Use among Adults in the US

Analyses of 2002 National Health Interview supplement on complementary and alternative medicine (NHI%AM) indicate that approximately 38 million adults in the US (18.9% of the population) used natural herbs or supplements in the preceding 12 months, but only one-third told their physician about this use. The objectives of this study are: (i) to determine subpopulation rates of patient–physician communication about herbal product and natural supplement use and (ii) to identify the relative influence of patient factors and interaction factors associated with patient-physician communication about herb and supplement use. Logistic secondary analysis was done by using the complementary and alternative medicine supplement of the 2002 National Health Interview Survey. Subjects were a random stratified sample of US adults who used herbs in the past 12 months (n = 5 196) and self-reported rates of disclosure to physicians about herb and supplement use. Results show that disclosure rates were significantly lower for males, younger adults, racial and ethnic minorities and less intensive users of medical care. Across subpopulations, disclosure was the exception rather than the norm. Given the potential risks of delayed or inappropriate treatment and adverse drug reactions and interactions, physicians should be aware of herb and supplement use and counsel patients on the potential risks and benefits of these treatments