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B Paredes

Publications and source records attributed to B Paredes.

12 recordsLinked to original sources
PubMed2006

Free fermion antibunching in a degenerate atomic Fermi gas released from an optical lattice.

Noise in a quantum system is fundamentally governed by the statistics and the many-body state of the underlying particles. The correlated noise observed for bosonic particles (for example, photons or bosonic neutral atoms) can be explained within a classical field description with fluctuating phases; however, the anticorrelations ('antibunching') observed in the detection of fermionic particles have no classical analogue. Observations of such fermionic antibunching are scarce and have been confined to electrons and neutrons. Here we report the direct observation of antibunching of neutral fermionic atoms. By analysing the atomic shot noise in a set of standard absorption images of a gas of fermionic (40)K atoms released from an optical lattice, we find reduced correlations for distances related to the original spacing of the trapped atoms. The detection of such quantum statistical correlations has allowed us to characterize the ordering and temperature of the Fermi gas in the lattice. Moreover, our findings are an important step towards revealing fundamental fermionic many-body quantum phases in periodic potentials, which are at the focus of current research.

Journal Article↗
PubMed2006

Rheological behavior and organoleptic effects of ovalbumin addition in yogurt mousse production.

Yogurt mousse is a novel, high added-value dairy product that has been well received by the market. This paper presents a study of the effect of the addition of ovalbumin to the product on its rheological and organoleptic qualities. The ovalbumin was previously separated from egg white with a high grade of purity using an ion exchange resin synthesized by the authors. Diverse rheological tests at different temperatures and corresponding sensorial assessments were conducted to compare samples without and with added ovalbumin. The obtained results confirm that the product is viscoelastic and combines the properties of foams and emulsions; the elastic component is greater than the viscous component. Moreover, at temperatures ranging from 5 to 15 degrees C, a usual interval of consumption, the product behaves rheologically in a similar way. Conversely, the addition of ovalbumin under the assayed conditions also makes the elastic character of the product increase at a given temperature. Finally, the sensorial assessment tests and determinations of stability and volume yield enabled us to verify that the addition of ovalbumin at an amount of 1.3% hardly alters the stability, resistance to shear stress, or the texture and improves the degree of foaming. Therefore, the product with additive is of good commercial quality.

Chromatography, Ion Exchange↗
PubMed2005

Exploiting quantum parallelism to simulate quantum random many-body systems.

We present an algorithm that exploits quantum parallelism to simulate randomness in a quantum system. In our scheme, all possible realizations of the random parameters are encoded quantum mechanically in a superposition state of an auxiliary system. We show how our algorithm allows for the efficient simulation of dynamics of quantum random spin chains with known numerical methods. We propose an experimental realization based on atoms in optical lattices in which disorder could be simulated in parallel and in a controlled way through the interaction with another atomic species.

Journal Article↗
PubMed2003

From Cooper pairs to Luttinger liquids with bosonic atoms in optical lattices.

We propose a scheme to observe strongly correlated fermionic phenomena with bosonic atoms in optical lattices. For different values of the sign and strength of the scattering lengths, it is possible to reach either a "superconducting" regime, where the system exhibits atomic pairing, or a Luttinger liquid behavior. We identify the range of parameters where these phenomena appear, illustrate our predictions with numerical calculations, and show how to detect the presence of pairing.

Journal Article↗
PubMed2003

Use of cocaine by secondary school students in northern Spain.

AIM: To describe the prevalence of cocaine and other drug use in secondary school students in Oviedo (Asturias, Northern Spain) and determine the personality features and levels of sensation seeking in cocaine users. METHODS: 2,862 secondary school students (mean age +/- SD = 15.87+/-1.48 years; 50.6% males) were interviewed during the 1998-1999 academic year. For evaluation, the World Health Organization questionnaire for drug consumption, the Eysenck Personality Questionnaire (EPQ) for adults and the Zuckerman Sensation Seeking Scale were used. RESULTS: The prevalence of lifetime, previous year and previous month cocaine use among secondary school students was 6.1, 4.9 and 2.7%, respectively. Cocaine ranked sixth among illicit drugs ever used by this population. Once individuals had used cocaine for the first time, they were likely to use it again (44.8% of those who had ever used cocaine reported that they had done so in the previous month). Compared to students who had never used cocaine (but who may have used other substances), cocaine users had a more extensive drug abuse history. Students who had used cocaine at some point during their lifetime scored significantly higher on the EPQ psychoticism subscale and reported higher levels of sensation seeking. CONCLUSIONS: There is a significant rate of cocaine consumption amongst secondary school students of both sexes. Cocaine users are polyconsumers of other substances, both legal and illicit. Those who consume cocaine have a different psychological profile, characterized by high sensation seeking and high levels of psychoticism.

Adolescent↗
PubMed2001

1/2-anyons in small atomic Bose-Einstein condensates.

We discuss a way of creating, manipulating, and detecting anyons in rotating Bose-Einstein condensates consisting of a small number of atoms. By achieving a quasidegeneracy in the atomic motional states we drive the system into a 1/2-Laughlin state for fractional quantum Hall bosons. Localized 1/2-quasiholes can be created by focusing lasers at the desired positions. We show how to manipulate these quasiholes in order to probe directly their 1/2-statistics.

Journal Article↗
PubMed2001

[Efficacy of topical povidone-iodine applied the day before cataract surgery to reduce conjunctival flora].

OBJECTIVE: To evaluate the efficacy of the topical use of periocular and conjunctival povidone-iodine solution applied the day before cataract surgery to reduce conjunctival flora. PATIENTS AND METHODS: Randomized and prospective clinical trial with 82 patients. The treatment group (41 patients) received an application of topical 10% povidone-iodine solution on the periocular skin and instillation of topical 5% povidone-iodine solution on the forniceal conjunctiva the day before and one hour before surgery. The control group (41 patients) only received the usual perioperative disinfectant. Conjunctival smears were obtained from in all patients at the end of the surgery and these were sent to the Microbiology Laboratory for culture. RESULTS: In the treatment group 1 positive culture was found in the 41 eyes (2.4%). In the control group, there were positive cultures in 6 out of 41 eyes (14.6%). The difference is statistically significant (p<0.05). CONCLUSIONS: The disinfecting of the periocular skin with 10% povidone-iodine solution and of the conjunctiva with 5% povidone-iodine solution the day before and one hour before cataract surgery is effective in reducing conjunctival bacterial colonization compared with perioperative disinfection alone.

Administration, Topical↗
PubMed1998

[Spitz nevus and Reed nevus: simulating melanoma in adults].

One hundred and three cases of Spitz nevi were reviewed, 36% of these patients were adults. The lesions in children occurred primarily on the face and secondarily on the trunk followed by the extremities. In adults, they affect the legs in women, and the trunk in men as does malignant melanoma. Clinically they were diagnosed more frequently as Spitz nevi in children and adolescents than in adults. Spitz nevi were most commonly mistaken clinically for "common" melanocytic nevus, hemangioma, verruca, fibrous histiocytoma, molluscum contagiosum, granuloma pyogenicum, keloid, and melanoma. Histologically, there are various expressions of Spitz nevi, but they are usually compound melanocytic nevi with little pigmentation and typically large spindle- and/or epithelioid melanocytes. There are only small histopathological differences between Spitz nevi in childhood and adulthood: one important feature rarely seen in Spitz nevi of adults is multiple mitotic figures at the dermo-epidermal junction but rarely at the base of the melanocytic nevus. Nevus Reed is considered to possibly be a distinctly pigmented variant of Spitz nevus.

Adolescent↗
PubMedDate not supplied

Egg-white protein fractionation using new weak anion-exchange resins based on poly(glycidyl methacrylate-co-ethylendimethacrylate). Preparation and characterization.

A new formulation for a poly(glycidyl methacrylate-co-ethylendimethacrylate)-based resin with a 11:9 proportion of monomer to crosslinker is developed and amino-functionalized in order to obtain new particulate materials suitable for egg-white protein fractionation. Functionalization is carried out using three different chemical reagents: diethylamine (DEA), DEA-tetrahydrofuran (THF) (1:1), and concentrated ammonia. The ammonia- and DEA-THF-treated polymers are used to fractionate egg-white proteins, in particular lysozyme and ovalbumin, by anion-exchange chromatography in packed column experiments, the latter resin showing better performances. Finally, both supports, working at semipreparative scale and step-gradient elution, separate pure ovalbumin with a yield of 83%.

Anion Exchange Resins↗