Transient dynamics of a superconducting nonlinear oscillator

We investigate the transient dynamics of a lumped-element oscillator based on a dc superconducting quantum interference device (SQUID). The SQUID is shunted with a capacitor forming a nonlinear oscillator with resonance frequency in the range of several GHz. The resonance frequency is varied by tuning the Josephson inductance of the SQUID with on-chip flux lines. We report measurements of decaying oscillations in the time domain following a brief excitation with a microwave pulse. The nonlinearity of the SQUID oscillator is probed by observing the ringdown response for different excitation amplitudes while the SQUID potential is varied by adjusting the flux bias. Simulations are performed on a model circuit by numerically solving the corresponding Langevin equations incorporating the SQUID potential at the experimental temperature and using parameters obtained from separate measurements characterizing the SQUID oscillator. Simulations are in good agreement with the experimental observations of the ringdowns as a function of applied magnetic flux and pulse amplitude. We observe a crossover between the occurrence of ringdowns close to resonance and adiabatic following at larger detuning from the resonance. We also discuss the occurrence of phase jumps at large amplitude drive. Finally, we briefly outline prospects for a readout scheme for superconducting flux qubits based on the discrimination between ringdown signals for different levels of magnetic flux coupled to the SQUID.Comment: 15 pages, 9 figure

Microstrip superconducting quantum interference device amplifiers with submicron Josephson junctions: enhanced gain at gigahertz frequencies

We present measurements of an amplifier based on a dc superconducting quantum interference device (SQUID) with submicron Al-AlOx-Al Josephson junctions. The small junction size reduces their self-capacitance and allows for the use of relatively large resistive shunts while maintaining nonhysteretic operation. This leads to an enhancement of the SQUID transfer function compared to SQUIDs with micron-scale junctions. The device layout is modified from that of a conventional SQUID to allow for coupling signals into the amplifier with a substantial mutual inductance for a relatively short microstrip coil. Measurements at 310 mK exhibit gain of 32 dB at 1.55 GHz.Comment: Version with high resolution figures at: http://physics.syr.edu/~bplourde/bltp-publications.ht

Ultrasound attenuation and a P-B-T phase diagram of superfluid 3He in 98% aerogel

Longitudinal sound attenuation measurements in superfluid 3He in 98% aerogel were conducted at pressures between 14 and 33 bar and in magnetic fields up to 4.44 kG. The temperature dependence of the ultrasound attenuation in the A-like phase was determined for the entire superfluid region exploiting the field induced meta-stable A-like phase at the highest field. In the lower field, the A-B transition in aerogel was identified by a smooth jump in attenuation on both cooling and warming. Based on the transitions observed on warming, a phase diagram as a function of pressure (P), temperature (T) and magnetic field (B) is constructed. We find that the A-B phase boundary in aerogel recedes in a drastically different manner than in bulk in response to an increasing magnetic field. The implications of the observed phase diagram are discussed.Comment: 9 pages, 13 figures, accepted to PR

An update on Cention N: An aesthetic direct bulk-fill restorative material

The demand for aesthetic restorative materials has increased in recent years. Glass ionomer cements (GIC), their modifications, and various composite restorative materials have been developed as direct tooth-coloured restorative materials. However, none of these materials can be compared to the properties of amalgam restorative materials. Recently, a new direct tooth-coloured, bulk-fill, and aesthetic restorative material, Cention N, was developed. This material is easy to handle and has properties similar to those of type-IX GIC. This article provides an update on the composition and properties of Cention N restorative material

Microstrip Superconducting Quantum Interference Device Amplifiers with Submicron Josephson Junctions: Enhanced Gain at Gigahertz Frequencies

We present measurements of an amplifier based on a dc superconducting quantum interference device (SQUID) with submicron Al-AlOx-Al Josephson junctions. The small junction size reduces their self-capacitance and allows for the use of relatively large resistive shunts while maintaining nonhysteretic operation. This leads to an enhancement of the SQUID transfer function compared to SQUIDs with micron-scale junctions. The device layout is modified from that of a conventional SQUID to allow for coupling signals into the amplifier with a substantial mutual inductance for a relatively short microstrip coil. Measurements at 310 mK exhibit gain of 32 dB at 1.55 GHz

Orbital glass and spin glass states of 3He-A in aerogel

Glass states of superfluid A-like phase of 3He in aerogel induced by random orientations of aerogel strands are investigated theoretically and experimentally. In anisotropic aerogel with stretching deformation two glass phases are observed. Both phases represent the anisotropic glass of the orbital ferromagnetic vector l -- the orbital glass (OG). The phases differ by the spin structure: the spin nematic vector d can be either in the ordered spin nematic (SN) state or in the disordered spin-glass (SG) state. The first phase (OG-SN) is formed under conventional cooling from normal 3He. The second phase (OG-SG) is metastable, being obtained by cooling through the superfluid transition temperature, when large enough resonant continuous radio-frequency excitation are applied. NMR signature of different phases allows us to measure the parameter of the global anisotropy of the orbital glass induced by deformation.Comment: 7 pages, 6 figures, Submitted to Pis'ma v ZhETF (JETP Letters

L-Proline as an efficient catalyst for synthesis of N-heterocyclic chalcones as potential antibacterial agents

855-859The condensation of 4-hydroxy-3-acetyl-1H-quinoline-2-one 1 and substitutedbenzaldehydes 2a-i in DMSO solution at room temperature yields quinolone chalcone derivatives 3a-i. l-Proline has been found to be an efficient catalyst for this condensation between 1 and 2. Only 5 mol% of the catalyst is necessary to achieve good yields of the products. Reactions proceed smoothly with variations of the substituents. 1 itself is synthesized by the acylation of commercially available methyl anthranilate 4 with acetoacetic ester 5 in refluxing xylene and subsequent Dieckman intramolcular cyclization of the intermediary 2-methoxycarbonylanilide 6

ELECTROSPUN NANOFIBROUS WOUND DRESSINGS: A REVIEW ON CHITOSAN COMPOSITE NANOFIBERS AS POTENTIAL WOUND DRESSINGS

Advancements in topical wound dressings led to the development of products to protect the wound and facilitate addressing special issues in healing and non-healing wounds. Rapidly growing interest in nanofiber research is leading to the development of potential candidates for wound dressing applications. Electrospinning nanofibers have been considered one of the effective materials in development of scaffolds for tissue engineering applications. Nanofibers mimic the extracellular matrix with their structural similarities, high surface area, and porosity, thereby enabling the effective delivery of antimicrobial agents in the wound milieu. Chitosan, an excellent biopolymer, is offering versatile applications as electrospun nanofibers due to the presence of its inherent properties like nontoxicity, biodegradability, biocompatibility, and antimicrobial nature, as well as its efficiency towards re‐epithelialization and regeneration of the granular layer of the wounds. The current review discusses the design and strategies used in the development of electrospun chitosan nanofibers, as well as the limitations of these strategies. This article provides the most recent information on the fabrication of chitosan composite nanofibrous materials and their applications for wound healing

In-vitro Effectiveness of Herbal Mouthwashes on the Force Degradation of Two Orthodontic E-chains

Background: Plaque build-up around fixed orthodontic appliances might lead to clinical problems. Even though mouthwashes are recommended during orthodontic treatment, the magnitude of force loading and unloading in elastomeric chains is significantly affected by alcohol-containing mouthwashes. Aim: To evaluate and compare the efficacy of herbal mouthwashes on the force degradation of two orthodontic E-chains. Materials and Methods: Chlorhexidine, Hiora-K and Triphala were used in the study. Ninety pieces of closed clear E-chains with five loops each of AO and 3M companies were collected and divided into three groups (n=30) namely Chlorhexidine, Hiora-K and Triphala. Each group was divided into two sub-groups based on the E-chain brands (n=15). On day 1, the original force was recorded by stretching the E-chain up to 25mm using universal testing machine and the load was recorded in kilograms and converted to grams. The E-chains were subjected to their respective mouthwashes daily for one minute. The force was again recorded on the 21st and 30th days. The obtained data were subjected to statistical analysis using SPSS 16.0 version. Results: The 3M E-chain showed a significant(p=0.000) difference compared with AO. Hiora and Triphala showed lesser force degradation than Chlorhexidine (p=0.013). Further, there was a significant (p=0.001) reduction in force degradation from baseline to the first month. Conclusion: Force degradation was more significant from the1st to the 21st day. 3M E-chain showed less force decay than AO E-chain. Hiora-K and Triphala mouthwash groups showed less force decay than the Chlorhexidine