Search results for "Freezing"

Melting and Freezing Lines for a Mixture of Charged Colloidal Spheres with Spindle-Type Phase Diagram

2010

We have measured the phase behavior of a binary mixture of like-charged colloidal spheres with a size ratio of 0.9 and a charge ratio of 0.96 as a function of particle number density n and composition p. Under exhaustively deionized conditions the aqueous suspension forms solid solutions of body centered cubic structure for all compositions. The freezing and melting lines as a function of composition show opposite behavior and open a wide, spindle shaped coexistence region. Lacking more sophisticated treatments, we model the interaction in our mixtures as an effective one-component pair energy accounting for number weighted effective charge and screening constant. Using this description, we…

Bactericidal activity of human milk: stability during storage

2016

Human milk provides infants with defensive factors against many illnesses. This study aims to analyse global bactericidal activity in fresh human milk and evaluate its stability in relation to milk manipulation and its possible alteration following refrigeration. Nineteen milk samples (mature milk) from 19 healthy women are analysed. Viability testing involving a strain of Escherichia coli NCTC 9111, serovar O111:K58(B4):H- was used to determine the bactericidal effect of human milk. Degree of bacteriolysis is calculated as the difference between E. coli counts in controls and in milk samples, expressed as a percentage of the control sample counts. An evaluation of the effect of refrigerati…

Freezing and storage at -20 °C provides adequate preservation of Toxoplasma gondii DNA for retrospective molecular analysis.

2014

Equipe EA MERS; International audience; Nucleic acid-based testing has become crucial for toxoplasmosis diagnosis. For retrospective (forensic or scientific) studies, optimal methods must be employed for DNA long-term storage. We compared Toxoplasma gondii detection before and after DNA storage using real-time PCR. No significant differences were found depending on duration or storage conditions at -20 °C or -80 °C.

Dynamic Effects on Reaction Rates in a Michael Addition Catalyzed by Chalcone Isomerase. Beyond the Frozen Environment Approach

2008

We present a detailed microscopic study of the dynamics of the Michael addition reaction leading from 6'-deoxychalcone to the corresponding flavanone. The reaction dynamics are analyzed for both the uncatalyzed reaction in aqueous solution and the reaction catalyzed by Chalcone Isomerase. By means of rare event simulations of trajectories started at the transition state, we have computed the transmission coefficients, obtaining 0.76 +/- 0.04 and 0.87 +/- 0.03, in water and in the enzyme, respectively. According to these simulations, the Michael addition can be seen as a formation of a new intramolecular carbon-oxygen bond accompanied by a charge transfer essentially taking place from the nu…

Experimental study on the free transplantation of mucosa and lyophilised dura to the oral cavity

1978

Summary The covering of epithelial defects in the oral cavity presents special problems in preprosthetic surgery, since special requisites for function and quality of mucosal grafts must be satisfied. In animal experiments mucosal defects in the oral cavity of 30 rabbits were repaired with free transplants of autologous mucosa and heterologous lyophilised dura. A comparative clinical and histological assessment of the healing processes showed that there was no essential difference between both methods. Considering the necessary second intervention, the infliction of a second wound, as well as the limited source of mucosa, our results show that the use of lyophilised dura in preprosthetic su…

Phenotypic characterization of the progenies of rice plants derived from cryopreserved calli

1999

The progenies of rice plants (Oryza sativa L.) differentiated from calli that had been cryopreserved and from control (non-cryopreserved) calli were used to study the influence of selection pressure during cryopreservation. The phenotypic evaluation of these progenies was based mainly on the response of seedlings and calli to freezing stress and on the characterization of protoplast and cell populations by flow cytometric analyses. The patterns of response to freezing stress, as well as the variations in some morphological and physiological cell parameters, were unrelated to the origin (cryopreserved or control calli) of the parental plants.

Acute electrocorticographic changes following localized cortical freezing in the cat. Preliminary report.

1968

Influence of different histologic preparation methods on preservation of tissue antigens in the immunofluorescent antibody technique.

1975

Observation of time-invariant coherence in a nuclear magnetic resonance quantum simulator

2016

The ability to live in coherent superpositions is a signature trait of quantum systems and constitutes an irreplaceable resource for quantum-enhanced technologies. However, decoherence effects usually destroy quantum superpositions. It was recently predicted that, in a composite quantum system exposed to dephasing noise, quantum coherence in a transversal reference basis can stay protected for an indefinite time. This can occur for a class of quantum states independently of the measure used to quantify coherence, and it requires no control on the system during the dynamics. Here, such an invariant coherence phenomenon is observed experimentally in two different setups based on nuclear magne…

Multioverlap Simulations of the 3D Edwards-Anderson Ising Spin Glass

1997

We introduce a novel method for numerical spin glass investigations: Simulations of two replica at fixed temperature, weighted such that a broad distribution of the Parisi overlap parameter $q$ is achieved. Canonical expectation values for the entire $q$-range (multi-overlap) follow by re-weighting. We demonstrate the feasibility of the approach by studying the $3d$ Edwards-Anderson Ising ($J_{ik}=\pm 1$) spin glass in the broken phase ($\beta=1$). For the first time it becomes possible to obtain reliable results about spin glass tunneling barriers. In addition, as do some earlier numerical studies, our results support that Parisi mean field theory is valid down to $3d$.