Your browser doesn't support javascript.
loading
Show: 20 | 50 | 100
Results 1 - 20 de 21
Filter
1.
Phys Rev Lett ; 125(23): 237202, 2020 Dec 04.
Article in English | MEDLINE | ID: mdl-33337211

ABSTRACT

The correlation length ξ, a key quantity in glassy dynamics, can now be precisely measured for spin glasses both in experiments and in simulations. However, known analysis methods lead to discrepancies either for large external fields or close to the glass temperature. We solve this problem by introducing a scaling law that takes into account both the magnetic field and the time-dependent spin-glass correlation length. The scaling law is successfully tested against experimental measurements in a CuMn single crystal and against large-scale simulations on the Janus II dedicated computer.

2.
ACS Appl Mater Interfaces ; 12(38): 42622-42633, 2020 Sep 23.
Article in English | MEDLINE | ID: mdl-32568508

ABSTRACT

Cu-based metal-organic framework (MOF) microdevices are applied in sampling and preconcentration of nerve agents (NAs) diluted in gaseous streams. An in situ electrochemical-assisted synthesis of a Cu-benzene-1,3,5-tricarboxylate (BTC) thick film is carried out to functionalize a Cu-modified glass substrate. This simple, rapid, reproducible, and easy-to-integrate MOF synthesis approach enables the microfabrication of functional micro-preconcentrators with a large Brunauer-Emmett-Teller (BET) surface area (above 2000 cm2) and an active pore volume (above 90 nL) for the efficient adsorption of nerve agent molecules along the microfluidic channel 2.5 cm in length. The equilibrium adsorption capacity of the bulk material has been characterized through thermogravimetric analysis after exposure to controlled atmospheres of a sarin gas surrogate, dimethyl methylphosphonate (DMMP), in both dry and humid conditions (30% RH at 293 K). Breakthrough tests at the ppm level (162 mg/m3) reveal equilibrium adsorption capacities up to 691 mg/g. The preconcentration performance of such µ-devices when dealing with highly diluted surrogate atmosphere, i.e., 520 ppbV (2.6 mg/m3) at 298 K, leads to preconcentration coefficients up to 171 for sample volume up to 600 STP cm3. We demonstrate the potentialities of Cu-BTC micro-preconcentrators as smart first responder tools for "on-field" detection of nerve agents in the gas phase at relevant conditions.


Subject(s)
Copper/chemistry , Metal-Organic Frameworks/chemistry , Nerve Agents/analysis , Tricarboxylic Acids/chemistry , Adsorption , Particle Size , Potentiometry , Surface Properties
3.
Phys Rev E ; 100(5-1): 050102, 2019 Nov.
Article in English | MEDLINE | ID: mdl-31869906

ABSTRACT

We explore the capacity of neural networks to detect a symmetry with complex local and non-local patterns: the gauge symmetry Z_{2}. This symmetry is present in physical problems from topological transitions to quantum chromodynamics, and controls the computational hardness of instances of spin-glasses. Here, we show how to design a neural network, and a dataset, able to learn this symmetry and to find compressed latent representations of the gauge orbits. Our method pays special attention to system-wrapping loops, the so-called Polyakov loops, known to be particularly relevant for computational complexity.

4.
Phys Rev Lett ; 120(26): 267203, 2018 Jun 29.
Article in English | MEDLINE | ID: mdl-30004737

ABSTRACT

Experiments on spin glasses can now make precise measurements of the exponent z(T) governing the growth of glassy domains, while our computational capabilities allow us to make quantitative predictions for experimental scales. However, experimental and numerical values for z(T) have differed. We use new simulations on the Janus II computer to resolve this discrepancy, finding a time-dependent z(T,t_{w}), which leads to the experimental value through mild extrapolations. Furthermore, theoretical insight is gained by studying a crossover between the T=T_{c} and T=0 fixed points.

5.
Phys Rev Lett ; 118(15): 157202, 2017 Apr 14.
Article in English | MEDLINE | ID: mdl-28452502

ABSTRACT

We first reproduce on the Janus and Janus II computers a milestone experiment that measures the spin-glass coherence length through the lowering of free-energy barriers induced by the Zeeman effect. Secondly, we determine the scaling behavior that allows a quantitative analysis of a new experiment reported in the companion Letter [S. Guchhait and R. Orbach, Phys. Rev. Lett. 118, 157203 (2017)].PRLTAO0031-900710.1103/PhysRevLett.118.157203 The value of the coherence length estimated through the analysis of microscopic correlation functions turns out to be quantitatively consistent with its measurement through macroscopic response functions. Further, nonlinear susceptibilities, recently measured in glass-forming liquids, scale as powers of the same microscopic length.

6.
Chem Commun (Camb) ; 52(7): 1494-7, 2016 Jan 25.
Article in English | MEDLINE | ID: mdl-26659642

ABSTRACT

FTIR spectra of (12)CO2 and (12)CO2 + (13)CO2 mixtures adsorbed on MIL-53(Al) reveal the formation of highly symmetric dimeric (CO2)2 species connected to two structural OH groups.

7.
CrystEngComm ; 17(7): 1693-1700, 2015 Feb 21.
Article in English | MEDLINE | ID: mdl-26246799

ABSTRACT

The effect of synthesis pH and H2O/EtOH molar ratio on the textural properties of different aluminium trimesate metal organic frameworks (MOFs) prepared in the presence of the well-known cationic surfactant cetyltrimethylammonium bromide (CTAB) at 120 °C was studied with the purpose of obtaining a MOF with hierarchical pore structure. Depending on the pH and the solvent used, different topologies were obtained (namely, MIL-96, MIL-100 and MIL-110). On the one hand, MIL-110 was obtained at lower temperatures than those commonly reported in the literature and without additives to control the pH; on the other hand, MIL-100 with crystallite sizes as small as 30 ± 10 nm could be easily synthesized in a mixture of H2O and EtOH with a H2O/EtOH molar ratio of 3.4 at pH 2.6 in the presence of CTAB. The resulting material displays a hierarchical porosity that combines the microporosity from the MOF and the non-ordered mesopores defined in between the MOF nanoparticles. Interestingly, the maximum of the pore size distribution could be varied between 3 and 33 nm. Finally, at pH 2.5 and using water as a solvent, platelets of MIL-96, a morphology never observed before for this MOF, were synthesized with a (001) preferential crystal orientation, the (001) plane running parallel to the bipyramidal cages of the MIL-96 topology.

8.
Article in English | MEDLINE | ID: mdl-25353474

ABSTRACT

We show in numerical simulations that a system of two coupled replicas of a binary mixture of hard spheres undergoes a phase transition in equilibrium at a density slightly smaller than the glass transition density for an unreplicated system. This result is in agreement with the theories that predict that such a transition is a precursor of the standard ideal glass transition. The critical properties are compatible with those of an Ising system. The relations of this approach to the conventional approach based on configurational entropy are briefly discussed.


Subject(s)
Models, Chemical , Models, Molecular , Models, Statistical , Nanospheres/chemistry , Nanospheres/ultrastructure , Phase Transition , Computer Simulation , Rheology/methods , Thermodynamics
9.
Respir Med ; 108(10): 1424-9, 2014 Oct.
Article in English | MEDLINE | ID: mdl-25256258

ABSTRACT

BACKGROUND: Abediterol (LAS100977) is a novel, long-acting ß2-agonist, in development for the once-daily treatment of asthma in combination with mometasone. Here we report the results of a Phase IIa trial of single doses of abediterol added to ongoing maintenance therapy (inhaled corticosteroids) in patients with persistent mild-to-moderate asthma. METHODS: This was a randomised, double-blind, placebo- and active-comparator-controlled, five-way crossover study. Male patients (18-70 years) with a clinical diagnosis of persistent asthma received abediterol (5, 10 and 25 µg), salmeterol and placebo, on top of ongoing maintenance therapy. Lung function was determined using spirometry and whole body plethysmography. The primary efficacy endpoint was change from baseline in trough forced expiratory volume in 1 s (FEV1) after a single dose. RESULTS: All three abediterol doses induced statistically significant increases in trough FEV1 vs placebo and salmeterol. Improvements in other lung function parameters were also statistically significantly greater with all abediterol doses vs both placebo (p < 0.0001) and salmeterol (p < 0.05) than the first assessment at 5 min post-dose. These improvements were sustained to 36 h post-dose. The profile of treatment-emergent adverse events judged as related to abediterol was consistent with that seen after adrenergic stimulation and occurred exclusively in patients who received abediterol 10 µg or 25 µg. CONCLUSIONS: This first-in-patient study revealed the potent, rapid and long-acting bronchodilatory effect of abediterol in patients with persistent mild-to-moderate asthma together with an overall good safety and tolerability profile. Further studies are now underway to establish the optimal efficacy-safety-tolerability profile for this compound.


Subject(s)
Adrenergic beta-2 Receptor Agonists/therapeutic use , Asthma/drug therapy , Quinolones/therapeutic use , Adolescent , Adrenergic beta-2 Receptor Agonists/administration & dosage , Adult , Aged , Albuterol/analogs & derivatives , Albuterol/therapeutic use , Cross-Over Studies , Double-Blind Method , Forced Expiratory Volume/physiology , Humans , Male , Middle Aged , Plethysmography, Whole Body , Quinolones/administration & dosage , Salmeterol Xinafoate , Spirometry , Treatment Outcome , Young Adult
10.
Article in English | MEDLINE | ID: mdl-24730822

ABSTRACT

We study the off-equilibrium dynamics of the three-dimensional Ising spin glass in the presence of an external magnetic field. We have performed simulations both at fixed temperature and with an annealing protocol. Thanks to the Janus special-purpose computer, based on field-programmable gate array (FPGAs), we have been able to reach times equivalent to 0.01 s in experiments. We have studied the system relaxation both for high and for low temperatures, clearly identifying a dynamical transition point. This dynamical temperature is strictly positive and depends on the external applied magnetic field. We discuss different possibilities for the underlying physics, which include a thermodynamical spin-glass transition, a mode-coupling crossover, or an interpretation reminiscent of the random first-order picture of structural glasses.

11.
Phys Rev Lett ; 108(16): 165701, 2012 Apr 20.
Article in English | MEDLINE | ID: mdl-22680734

ABSTRACT

We present a tethered Monte Carlo simulation of the crystallization of hard spheres. Our method boosts the traditional umbrella sampling to the point of making practical the study of constrained Gibbs' free energies depending on several crystalline order parameters. We obtain high-accuracy estimates of the fluid-crystal coexistence pressure for up to 2916 particles (enough to accommodate fluid-solid interfaces). We are able to extrapolate to infinite volume the coexistence pressure [p(co)=11.5727(10)k(B)T/σ(3)] and the interfacial free energy [γ({100})=0.636(11)k(B)T/σ(2)].

12.
Pulm Pharmacol Ther ; 25(3): 248-53, 2012 Jun.
Article in English | MEDLINE | ID: mdl-22497752

ABSTRACT

This Phase IIb, double-blind, double-dummy, placebo- and active-comparator-controlled crossover study (ClinicalTrials.gov identifier: NCT01120093) assessed efficacy and safety of three doses of aclidinium bromide in patients with moderate to severe chronic obstructive pulmonary disease. Patients were randomised to one of five treatment sequences each consisting of twice-daily (BID) aclidinium 100 µg, 200 µg, 400 µg (via Genuair®*), formoterol 12 µg (via Aerolizer®) and matched placebo for 7 days, with a 5- to 9-day washout period. Primary endpoint was mean change from baseline in forced expiratory volume in 1 s (FEV1) normalised area under the curve (AUC)0-12 on Day 7. Secondary endpoints were: change from baseline in FEV1 normalised AUC12-24, FEV1 normalised AUC0-24 and morning pre-dose FEV1 on Day 7. Adverse events were monitored throughout the study. Of 79 randomised patients, 68 (86.1%) completed the study. After 7 days of treatment, aclidinium and formoterol produced statistically significantly greater changes from baseline in FEV1 normalised AUC0-12 vs placebo (p<0.0001). FEV1 normalised AUC12-24, FEV1 normalised AUC0-24, and morning pre-dose FEV1 were also statistically significantly greater with all aclidinium doses vs placebo (p<0.0001). Improvements in primary and secondary endpoints were statistically significantly greater with aclidinium 400 µg vs 100 µg. The safety profile of aclidinium was comparable to placebo. These results demonstrated that twice-daily aclidinium produced dose-dependent clinically meaningful improvements in FEV1 compared with placebo. This study also confirmed the use of an aclidinium BID dosing regimen and established aclidinium 200 µg and 400 µg as suitable doses for further investigation in Phase III trials.


Subject(s)
Bronchodilator Agents/therapeutic use , Ethanolamines/therapeutic use , Pulmonary Disease, Chronic Obstructive/drug therapy , Tropanes/therapeutic use , Administration, Inhalation , Aged , Area Under Curve , Bronchodilator Agents/administration & dosage , Bronchodilator Agents/adverse effects , Cross-Over Studies , Dose-Response Relationship, Drug , Double-Blind Method , Ethanolamines/administration & dosage , Ethanolamines/adverse effects , Female , Forced Expiratory Volume , Formoterol Fumarate , Humans , Male , Middle Aged , Pulmonary Disease, Chronic Obstructive/physiopathology , Treatment Outcome , Tropanes/administration & dosage , Tropanes/adverse effects
13.
Phys Rev E Stat Nonlin Soft Matter Phys ; 82(2 Pt 1): 021501, 2010 Aug.
Article in English | MEDLINE | ID: mdl-20866812

ABSTRACT

We study a polydisperse soft-spheres model for colloids by means of microcanonical Monte Carlo simulations. We consider a polydispersity as high as 24%. Although solidification occurs, neither a crystal nor an amorphous state are thermodynamically stable. A finite size scaling analysis reveals that in the thermodynamic limit: (a) the fluid-solid transition is rather a crystal-amorphous phase-separation, (b) such phase-separation is preceded by the dynamic glass transition, and (c) small and big particles arrange themselves in the two phases according to a complex pattern not predicted by any fractionation scenario.


Subject(s)
Chemical Fractionation/methods , Colloids/chemistry , Colloids/isolation & purification , Models, Chemical , Computer Simulation
14.
Phys Rev Lett ; 105(17): 177202, 2010 Oct 22.
Article in English | MEDLINE | ID: mdl-21231075

ABSTRACT

We numerically study the aging properties of the dynamical heterogeneities in the Ising spin glass. We find that a phase transition takes place during the aging process. Statics-dynamics correspondence implies that systems of finite size in equilibrium have static heterogeneities that obey finite-size scaling, thus signaling an analogous phase transition in the thermodynamical limit. We compute the critical exponents and the transition point in the equilibrium setting, and use them to show that aging in dynamic heterogeneities can be described by a finite-time scaling ansatz, with potential implications for experimental work.

15.
J Colloid Interface Sci ; 333(2): 497-502, 2009 May 15.
Article in English | MEDLINE | ID: mdl-19264323

ABSTRACT

Solvent uptake, hydraulic and electroosmotic permeabilities, true cation transport number, effective fixed charge concentration, and limiting current values have been determined in aqueous LiCl solutions for three commercial cation-exchange membranes with different morphologies and similar electric properties. The differences found in the equilibrium and transport properties of the membranes have been analyzed on the basis of their different structures. The experimental results show that the membrane morphology has an influence on the effect that the presence of an electrolyte has in the solvent uptake and in the liquid permeation. Differences have also been found in the polarization concentration effects, and on the loss of the membrane selectivity with the increase of the electrolyte concentration.

16.
Acta pediatr. esp ; 64(1): 30-31, ene. 2006. ilus
Article in Es | IBECS | ID: ibc-043529

ABSTRACT

Se presenta el cado de un niño de siete años que sufre una gastroenteritis por Salmonella D9. A los quince dias de empezar la clínica, aparecen mialgias e inestabilidad en la marcha, dolor testicular y lesiones cutáneas. Fue diagnosticado de ataxia cerebelosa aguda, orquiepididimitis y eritema nodoso. Aunque todas estas complicaciones están descritas en la bibliogradía, resulta excepcional encontrarlas juntas en un mismo paciente


We present the case of a seve-year-old boy with gastroenteritis caused by Salmonella D9. Fifteen days after the clinical onset, he began to develop muscular pain, unsteady gait, testicular pain and skin lesions. The diagnoses were acute cerebellar ataxia, epididymo-orchitis and erythema nodosum. Each of these complications has been reported in the literature, but it is highly unusual to find all of them in the same patient


Subject(s)
Male , Child , Humans , Cerebellar Ataxia/complications , Cerebellar Ataxia/diagnosis , Cerebellar Ataxia/drug therapy , Erythema Nodosum/complications , Erythema Nodosum/drug therapy , Gastroenteritis/complications , Gastroenteritis/drug therapy , Trimethoprim, Sulfamethoxazole Drug Combination/therapeutic use , Epididymitis/complications , Orchitis/complications , Salmonella , Salmonella/pathogenicity , Gastroenteritis/diagnosis , Quinolones/therapeutic use , Anti-Inflammatory Agents/therapeutic use , Fever/etiology , Fever/therapy , Arthralgia/complications , Arthralgia/diagnosis , Arthralgia/therapy
17.
J Colloid Interface Sci ; 288(2): 540-7, 2005 Aug 15.
Article in English | MEDLINE | ID: mdl-15927624

ABSTRACT

The volume flow of methanol-water potassium chloride solutions through a Nafion membrane originated by the simultaneous action of electric potential and pressure gradients has been measured at different percentages of methanol. Measurements were conducted when both gradients act in the same and in the opposite directions under different experimental conditions. The results indicate that the simultaneous action of the pressure and potential differences originates a total flow different from the sum of the individual electroosmotic and permeation flows due to each force acting separately. The application of the irreversible thermodynamics theory, which includes second-order terms, allowed the study of the influence of the composition of the solutions on the determination of the different phenomenological coefficients.

18.
J Colloid Interface Sci ; 278(2): 410-22, 2004 Oct 15.
Article in English | MEDLINE | ID: mdl-15450461

ABSTRACT

Dense flat-sheet membranes were prepared from poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) using the casting solvents chloroform and 1,1,2-trichloroethylene. X-ray diffraction, tapping mode atomic force microscopy (TM-AFM), and contact angle studies were used to characterize the membranes. The surface energy and the solubility parameters of the PPO membranes were determined from the measured contact angles and compared with the predicted ones from the group contribution method. Swelling experiments and pervaporation separation of methanol from its mixture with ethylene glycol over the entire range of concentration, 0-100%, were conducted using these membranes. Flory-Huggins theory was used to predict the sorption selectivity. The results are discussed in terms of the solubility parameter approach and as function of the morphological characteristics of the membranes. It was found that PPO membranes prepared with chloroform exhibited better pervaporation performance than PPO membranes prepared with 1,1,2-trichloroethylene.

19.
J Colloid Interface Sci ; 277(1): 176-83, 2004 Sep 01.
Article in English | MEDLINE | ID: mdl-15276055

ABSTRACT

The volume flow through a Nafion membrane originated by the simultaneous action of an electric potential difference and a pressure difference has been measured using aqueous KCl solutions under different experimental conditions. The behavior has been analyzed when both gradients act in the same and in the opposite sense. The results indicate that the simultaneous action of the pressure and potential differences originates a total flow different from the sum of the electroosmotic and permeation flows due to each force acting separately. The application of irreversible thermodynamics, which includes second-order terms, allowed the determination of the phenomenological coefficients. Moreover, from these values, the equivalent pore radius was estimated on the assumption that the membrane is a porous medium filled with an internal solution.

20.
J Colloid Interface Sci ; 268(2): 476-81, 2003 Dec 15.
Article in English | MEDLINE | ID: mdl-14643249

ABSTRACT

The volume flux through a cation-exchange membrane (Nafion 117) separating two equal electrolyte water-methanol solutions as a function of the pressure difference was determined under different experimental conditions. The results show that permeation rates through the membrane are strongly dependent on the methanol content of the solutions, thus the value of the flux increases when the methanol percentage increases. The effect of the electrolyte concentration of the solution on the membrane permeability is less important, although its influence becomes significant at low electrolyte concentration and high methanol content on solvent. This behavior is explained in terms of the amount of solvent sorbed by the membrane. Typical flux behaviors observed with pressure difference are linear at low pressures, exhibiting a positive deviation at higher pressure difference values.

SELECTION OF CITATIONS
SEARCH DETAIL
...