Observation of first and second sound in a BKT superfluid.

Superfluidity in its various forms has been of interest since the observation of frictionless flow in liquid helium II1,2. In three spatial dimensions it is conceptually associated with the emergence of long-range order at a critical temperature. One of the hallmarks of superfluidity, as predicted by the two-fluid model3,4 and observed in both liquid helium5 and in ultracold atomic gases6,7, is the existence of two kinds of sound excitation-the first and second sound. In two-dimensional systems, thermal fluctuations preclude long-range order8,9; however, superfluidity nevertheless emerges at a non-zero critical temperature through the infinite-order Berezinskii-Kosterlitz-Thouless (BKT) transition10,11, which is associated with a universal jump12 in the superfluid density without any discontinuities in the thermodynamic properties of the fluid. BKT superfluids are also predicted to support two sounds, but so far this has not been observed experimentally. Here we observe first and second sound in a homogeneous two-dimensional atomic Bose gas, and use the two temperature-dependent sound speeds to determine the superfluid density of the gas13-16. Our results agree with the predictions of BKT theory, including the prediction of a universal jump in the superfluid density at the critical temperature.

Spin- and Momentum-Correlated Atom Pairs Mediated by Photon Exchange and Seeded by Vacuum Fluctuations.

Engineering pairs of massive particles that are simultaneously correlated in their external and internal degrees of freedom is a major challenge, yet essential for advancing fundamental tests of physics and quantum technologies. In this Letter, we experimentally demonstrate a mechanism for generating pairs of atoms in well-defined spin and momentum modes. This mechanism couples atoms from a degenerate Bose gas via a superradiant photon-exchange process in an optical cavity, producing pairs via a single channel or two discernible channels. The scheme is independent of collisional interactions, fast, and tunable. We observe a collectively enhanced production of pairs and probe interspin correlations in momentum space. We characterize the emergent pair statistics and find that the observed dynamics is consistent with being primarily seeded by vacuum fluctuations in the corresponding atomic modes. Together with our observations of coherent many-body oscillations involving well-defined momentum modes, our results offer promising prospects for quantum-enhanced interferometry and quantum simulation experiments using entangled matter waves.

Emergence of Isotropy and Dynamic Scaling in 2D Wave Turbulence in a Homogeneous Bose Gas.

We realize a turbulent cascade of wave excitations in a homogeneous 2D Bose gas and probe on all relevant time and length scales how it builds up from small to large momenta, until the system reaches a steady state with matching energy injection and dissipation. This all-scales view directly reveals the two theoretically expected cornerstones of turbulence formation-the emergence of statistical momentum-space isotropy under anisotropic forcing and the spatiotemporal scaling of the momentum distribution at times before any energy is dissipated.

Excessive noise levels are noted in kindergarten classrooms in the island of Crete.

Ambient noise in classrooms may present a serious obstacle to the academic achievement of children. There is relatively little information on noise levels in teaching facilities in Greece and particularly in the island of Crete. The purpose of this study was to provide objective data on the internal noise levels inside kindergartens in Crete. The study was conducted in the city of Heraklion in the island of Crete, Greece. Ten kindergartens were selected and a total of 18 classrooms were chosen. Noise levels were measured in occupied and unoccupied classrooms. Noise levels in occupied classrooms ranged from 71.6 to 82.9 dBA with an average of 75.8 dBA. Noise levels in empty classrooms varied from 48.2 to 59.6 dBA with an average of 53.1 dBA. All values are well above international standards. Excessive classroom noise seems to be very common in kindergartens. Results may indicate that school facilities are not built in compliance with international standards. School administrators and local authorities should become aware of the problem, and make any necessary interventions to improve the learning capabilities of children.

Correlation between LGR5 stem cells and location of tumor as well as age, sex and metastasis in colon adenocarcinoma.

PURPOSE: G-protein receptors belong to a large family of receptors which includes more than 800 kinds. An interest for these receptors arose upon noticing their expression on skin, intestine and breast stem cells. METHODS: We examined the tissues of 53 patients who had been diagnosed with adenocarcinoma of the colon. There were no exclusion criteria. We measured the expression levels of LGR5 by immunohistochemistry and we correlated those and the location of the colon primary tumor with the age, sex and the metastatic potential. RESULTS: The median values of the two groups- the orthosigmoid and the other colon location- were 1 and 3.5 respectively with no statistical significance and with p=0.132. Spearman Rho indicated no statistical significance between the expression of LGR5 and age with p=0.219. Moreover, the Mann-Whitney U test showed no statistical significance between LGR5 and sex with p=0.778. Fisher's test, however, showed a statistically significant result between metastasis and expression of LGR5 with p=0.025. CONCLUSION: It becomes apparent that patients with increased expression of these two markers are characterized by a more aggressive form of the disease with an increased rate of metastasis. Also, interactions on both paths lead to a simultaneous overexpression, thus proving the diversity of carcinogenic pathways. Racial and other factors are not affected, and ultimately the need to target these indicators in treatment protocols is imperative.

Benign paroxysmal positional vertigo: 10-year experience in treating 592 patients with canalith repositioning procedure.

OBJECTIVE: To assess the long-term efficacy of canalith repositioning procedure (CRP) in the treatment of patients with benign paroxysmal positional vertigo (BPPV). BACKGROUND: Alternative theories for the pathophysiology of BPPV have been redefined in the past few years. CRP is considered to be the standard technique for its management. However, long-term follow-up results have been minimally reported in the literature. PATIENTS/METHODS: Five hundred ninety-two patients, 290 (49%) men and 302 (51%) women, were enrolled in this prospective study; their ages ranged from 18 to 84 (mean 59) years. At the time of their first examination, patients reported the duration of symptoms varied from 1 day to 18 months. Inclusion criteria were patient history compatible with BPPV and positive provocative maneuver (either Dix-Hallpike or Roll test). A variant of Epley and Barbeque maneuver was used. The Epley maneuver was used for posterior and anterior canal involvement, and "Barbeque roll" was used for horizontal canal involvement. Short-term follow-up was obtained 48 hours and 7 days after initial treatment, whereas long-term follow-up was obtained at repeated 6 month intervals. RESULTS: The posterior semicircular canal was involved in 521 (88%) patients treated, whereas the horizontal and anterior semicircular canals were involved in 59 (10%) and 12 (2%) patients, respectively. Symptoms subsided immediately in 497 (84%) patients. In 77 (13%) patients, the Dix-Hallpike maneuver remained positive after 48 hours, and CRP was performed again. Patients' mean follow-up was 46 months; 544 (92%) of 592 patients treated reported no symptoms of vertigo. CONCLUSION: Our data, based on long-term follow-up, suggest that CRP remains an efficient and long-lasting noninvasive treatment for BPPV.

Application of a ketogenic diet in children with autistic behavior: pilot study.

A pilot prospective follow-up study of the role of the ketogenic diet was carried out on 30 children, aged between 4 and 10 years, with autistic behavior. The diet was applied for 6 months, with continuous administration for 4 weeks, interrupted by 2-week diet-free intervals. Seven patients could not tolerate the diet, whereas five other patients adhered to the diet for 1 to 2 months and then discontinued it. Of the remaining group who adhered to the diet, 18 of 30 children (60%), improvement was recorded in several parameters and in accordance with the Childhood Autism Rating Scale. Significant improvement (> 12 units of the Childhood Autism Rating Scale) was recorded in two patients (pre-Scale: 35.00 +/- 1.41[mean +/- SD]), average improvement (> 8-12 units) in eight patients (pre-Scale: 41.88 +/- 3.14[mean +/- SD]), and minor improvement (2-8 units) in eight patients (pre-Scale: 45.25 +/- 2.76 [mean +/- SD]). Although these data are very preliminary, there is some evidence that the ketogenic diet may be used in autistic behavior as an additional or alternative therapy.

Transtympanic iontophoresis of gadopentetate dimeglumine: Preliminary results.

OBJECTIVE: We sought to demonstrate the feasibility of using iontophoresis to deliver pharmaceutical agents into the middle and inner ear for the treatment of middle and inner ear diseases, which is proved in this study by the successful iontophoresis of the ferromagnetic contrast agent gadopentetate dimeglumine. Study design and setting Eight rabbits were iontophoresed using gadopentetate dimeglumine solution 469 mg/mL. Then, all rabbits underwent magnetic resonance imaging for the detection of gadopentetate dimeglumine in the middle and inner ear structures. The study was conducted in the tertiary referral center the University Hospital of Crete. RESULTS: The high signal intensity of the gadopentetate dimeglumine solution was demonstrated within the middle ear cavity and inner ear structures of all iontophoresed ears and in none of the noniontophoresed ones. CONCLUSIONS: Transtympanic iontophoresis could be an effective method for the passage of pharmaceutical agents into the middle and inner ear for the treatment of middle and inner ear diseases.

The role of laser assisted tympanostomy (LAT) in treating allergic children with chronic serous otitis media.

OBJECTIVES: To assess various prognostic factors influencing the outcome in paediatric patients with serous otitis media, who have undergone laser assisted tympanostomy without ventilation tube placement. Emphasis is given to children with allergies who underwent the procedure. METHOD: Laser assisted tympanostomy was performed on a total of 130 ears (92 individuals) with chronic otitis media with effusion. To determine the quality of patient outcome, the following parameters were evaluated: external auditory canal anatomy, type of anaesthesia used, tympanic membrane and middle ear fluid characteristics, myringotomy size, a history of allergies and the laser device parameters. RESULTS: Multivariable statistical analysis demonstrated that the presence of allergies in children with chronic serous otitis media is significantly correlated with a poor outcome (P < 0.0047). Moreover, the presence of a thick tympanic membrane and/or high viscosity (glue) fluid in the middle ear cavity can also independently influence patient outcome (P < 0.025). Simultaneous adenoidectomy and/or tonsillectomy, type of anaesthesia (general versus local), external canal anatomy (wide or narrow) and sex, were not statistically important prognostic factors. The type of anaesthesia used, myringotomy size and the laser device parameters were not found to be associated with patient outcome. CONCLUSION: A history of allergies, the presence of a thick tympanic membrane and/or high viscosity fluid in the middle ear cavity are all contraindications for laser assisted tympanostomy without tympanostomy tubes, in children who suffer from chronic serous otitis media. The selection criteria for this procedure in the paediatric population are addressed in detail.

The cochlear implant programme in Crete: a nine year experience.

The aim of this study was to present data of the cochlear implant programme in Crete. Our series consists of 51 patients, 35 adults and 16 children, in a nine year period. The average age of our patients was 31 years (range from three to 68). The average duration of deafness among our patients was seven years (range from two to 22). Our series included 32 postlingual patients and 19 prelingual patients. The cause of deafness in our series was unknown in approximately 40 per cent of cases. Standard selection criteria and operative techniques were used for all cases. Postoperative programming and rehabilitation were performed according to the individual needs of each patient. Implantation was successful in all patients except one who had to undergo a second operation with good results. No major postoperative complications were noted, while minor complications included temporary facial weakness and undesired stimulation of the facial nerve during implant function in two and three patients, respectively. All patients showed significant improvement in perception and discrimination of sound and speech. Better results have been noted in prelingual patients under the age of six, as well as in postlingual adults with a recent history of deafness. As cochlear implant technology evolves and surgical techniques continue to improve, our department will continue its efforts to provide effective hearing rehabilitation of deaf children and adults in Crete.

Transtympanic iontophoresis with a biocompatible paramagnetic solution at MR imaging: experimental feasibility study in rabbits.

PURPOSE: To determine the feasibility of transtympanic iontophoresis in experimental animals with a paramagnetic contrast agent at magnetic resonance (MR) imaging. MATERIALS AND METHODS: Optimal MR sequence parameters and appropriate paramagnetic ion concentrations of a water and gadopentetate dimeglumine solution were initially assessed with phantoms. Iontophoresis was performed in left ears of five rabbits after the external auditory canals were filled with a solution of water and gadopentetate dimeglumine of optimal concentration, and right ears were used as controls. Signal-to-structural noise ratio (SSNR) and contrast-to-structural noise ratio (CSNR) were measured by using regions of interest, and the overall image quality was assessed subjectively. RESULTS: Spin-echo (SE) MR sequences were superior to gradient-echo (GRE) MR sequences in terms of SSNR, CSNR, and overall image quality. Highest SSNR and CSNR values were achieved with 2 mmol/L (2 mM) of gadopentetate dimeglumine solution with both SE (repetition time msec/echo time msec, 500/12; flip angle, 90 degrees ) and GRE (300/10; flip angle, 90 degrees ) sequences in both phantoms and animals. The high signal intensity of gadopentetate dimeglumine solution was recognized in middle ears, vestibules, and semicircular canals of all rabbit ears that had undergone iontophoresis and in none of the control ears. CONCLUSION: With the solution of water and gadopentetate dimeglumine, the maximum SSNR and CSNR with both SE and GRE MR imaging sequences were achieved. The solution can be transferred to the middle and inner ear cavities across an intact tympanic membrane by using transtympanic iontophoresis.