Confinement of Spin and Charge in High-Temperature Superconductors

By exploiting the internal gauge-invariance intrinsic to a spin-charge separated electron, we show that such degrees of freedom must be confined in two-dimensional superconductors experiencing strong inter-electron repulsion. We also demonstrate that incipient confinement in the normal state can prevent chiral spin-fluctuations from destroying the cross-over between strange and psuedo-gap regimes in under-doped high-temperature superconductors. Last, we suggest that the negative Hall anomaly observed in these materials is connected with this confinement effect.Comment: 12 pages, 1 postscript figure, to appear in PRB (RC), May 199

Aménagements hydro-agricoles et santé (vallée du fleuve Sénégal)

La ville de Richard-Toll offre sept types de points d'eau à sa population, allant du site ouvert non aménagé (fleuve) aux bornes offrant de l'eau canalisée. Les usagers y gèrent eux-mêmes leur réserve d'eau quotidienne. Pour évaluer l'effet du site d'approvisionnement et du comportement de l'usager sur la qualité de l'eau consommée, l'eau de 14 sites, représentant les sept types de points d'eau présents dans la ville, a été échantillonnée. De plus, quatre usagers ont été associés à chaque point d'eau, et leur eau a été analysée à domicile à trois reprises, soit après entreposage de moins d'une heure, de 8 heures et de 24 heures. Les analyses ont permis de déterminer la qualité bactériologique de l'eau (coliformes fécaux), qui s'est avérée être excellente (0-10 UCG par 100 ml) à 4 des 14 points d'eau, et mauvaise (101-500 UGC par 100 ml) ou très mauvaise (> 500 UGC par 100 ml) dans les autres cas. Après entreposage de moins d'une heure, l'eau à l'origine excellente a vu sa qualité se dégrader chez la moitié (8 des 16) des usagers, alors que l'eau de mauvaise et de très mauvaise qualité s'est améliorée chez 19 des 39 usagers. Durant l'entreposage quotidien normal de 24 heures, l'eau à l'origine d'excellente qualité s'est dégradée dans 14 des 16 cas, alors que l'eau à l'origine mauvaise ou très mauvaise, s'est améliorée de façon permanente dans 14 des 35 cas. La chloration de l'eau à domicile explique certaines améliorations (5 des 14 cas). Ces résultats démontrent que si la qualité dépend au départ du site d'approvisionnement, l'usager est en mesure de l'affecter de façon positive ou négative, et ce indépendamment de la situation de départ. (Résumé d'auteur

Microscopic origin of universality in Casimir forces

The microscopic mechanisms for universality of Casimir forces between macroscopic conductors are displayed in a model of classical charged fluids. The model consists of two slabs in empty space at distance $d$ containing classical charged particles in thermal equilibrium (plasma, electrolyte). A direct computation of the average force per unit surface yields, at large distance, the usual form of the Casimir force in the classical limit (up to a factor 2 due to the fact that the model does not incorporate the magnetic part of the force). Universality originates from perfect screening sum rules obeyed by the microscopic charge correlations in conductors. If one of the slabs is replaced by a macroscopic dielectric medium, the result of Lifshitz theory for the force is retrieved. The techniques used are Mayer expansions and integral equations for charged fluids.Comment: 31 pages, 0 figures, submitted to Journal of Statistical Physic

Антисиметричнi хвилi в системi двох паралельних стержнiв, перiодично пiдкрiплених жорсткими поперечними перегородками i зв'язаних з акустичним середовищем

Розглянуто можливiсть поширення антисиметричних гармонiчних хвиль у системi двох перiодично пiдкрiплених жорсткими поперечними перегородками паралельних пружних стержнiв. При цьому вважалося, що обмеженi стержнями й сусiднiми перегородками об'єми заповненi акустичним середовищем (газом), а самi стержнi коливаються протифазно. Iз застосуванням методу Флоке одержано вiдповiдне дисперсiйне рiвняння i проаналiзовано його коренi. Збуджена таким способом хвиля - еквiволюмiальна, тому внутрiшнє акустичне середовище вiдiграє тут роль приєднаної маси. Як наслiдок, у цьому випадку ефективна пружнiсть системи i вiдповiдна швидкiсть поширення хвилi виявилися значно нижчими, нiж при синфазних коливаннях стержнiв, якi супроводжуються об'ємними деформацiями газонаповнених камер. Одержаний результат дозволяє на якiсному рiвнi пояснити деякi експериментальнi данi стосовно хвильових властивостей пористих газонаповнених середовищ, зокрема, легеневої паренхiми.Рассмотрена возможность распространения антисимметричных гармонических волн в системе двух периодически подкрепленных жесткими поперечными перегородками параллельных упругих стержней. При этом считалось, что ограниченные стержнями и соседними перегородками объемы заполнены акустической средой, а сами стержни колеблются противофазно. С применением метода Флоке получено соответствующее дисперсионное уравнение и проанализированы его корни. Возбужденная таким способом волна - эквиволюмиальная, поэтому внутренняя акустическая среда играет здесь роль присоединенной массы. Как следствие, в этом случае эффективная упругость системы и соответствующая скорость распространения волны оказались значительно ниже, чем при синфазных колебаниях стержней, которые сопровождаются объемными деформациями газонаполненных камер. Полученный результат позволяет на качественном уровне объяснить некоторые экспериментальные данные, касающиеся волновых свойств пористых газонаполненных сред, в частности, легочной паренхимы.The paper deals with considering the possibility of antisymmetric harmonic wave propagation in the system of two elastic rods periodically supported by rigid transverse barriers. The volumes bounded by the rods and adjacent barriers were considered to be filled with an acoustic medium (gas), with rods performing an antiphase motion. With use of the Floquet method, the corresponding dispersion equation has been obtained and its roots have been analyzed. The wave, excited in such way, is an equivoluminal one, therefore, the internal acoustic medium plays the role of an equivalent mass. Hence, in this case the effective system elasticity parameter and corresponding wave propagation velocity are considerably lower than that occurring at the in-phase rod vibration, accompanying by volume deformations of the gas-filled cells. The obtained result allows the qualitative explanation of some experimental data concerning wave properties of gas-filled porous media, in particular, the parenchyma of the lung

CCR6+ Th cell populations distinguish ACPA positive from ACPA negative rheumatoid arthritis

Introduction: Patients with rheumatoid arthritis (RA) can be separated into two major subpopulations based on the absence or presence of serum anti-citrullinated protein antibodies (ACPAs). The more severe disease course in ACPA+ RA and differences in treatment outcome between these subpopulations suggest that ACPA+ and ACPA- RA are different disease subsets. The identification of T-helper (Th) cells specifically recognizing citrullinated peptides, combined with the strong association between HLA-DRB1 and ACPA positivity, point toward a pathogenic role of Th cells in ACPA+ RA. In this context we recently identified a potential pathogenic role for CCR6+ Th cells in RA. Therefore, we examined whether Th cell population distributions differ by ACPA status. Methods: We performed a nested matched case-control study including 27 ACPA+ and 27 ACPA- treatment-naive early RA patients matched for disease activity score in 44 joints, presence of rheumatoid factor, sex, age, duration of complaints and presence of erosions. CD4+CD45RO+ (memory) Th cell distribution profiles from these patients were generated based on differential chemokine receptor expression and related with disease duration. Results: ACPA status was not related to differences in total CD4+ T cell or memory Th cell proportions. However, ACPA+ patients had significantly higher proportions of Th cells expressing the chemokine receptors CCR6 and CXCR3. Similar proportions of CCR4+ and CCR10+ Th cells were found. Within the CCR6+ cell population, four Th subpopulations were distinguished based on differential chemokine receptor expression: Th17 (CCR4+CCR10-), Th17.1 (CXCR3+), Th22 (CCR4+CCR10+) and CCR4/CXCR3 double-positive (DP) cells. In particular, higher proportions of Th22 (p = 0.02), Th17.1 (p = 0.03) and CCR4/CXCR3 DP (p = 0.01) cells were present in ACPA+ patients. In contrast, ACPA status was not associated with differences in Th1 (CCR6-CXCR3+; p = 0.90), Th2 (CCR6-CCR4+; p = 0.27) and T-regulatory (CD25hiFOXP3+; p = 0.06) cell proportions. Interestingly, CCR6+ Th cells were inversely correlated with disease duration in ACPA- patients (R2 = -0.35; p < 0.01) but not in ACPA+ (R2 < 0.01; p = 0.94) patients. Conclusions: These findings demonstrate that increased peripheral blood CCR6+ Th cells proportions distinguish ACPA+ RA from ACPA- RA. This suggests that CCR6+ Th cells are involved in the differences in disease severity and tr

Comparing the Performance of Supported Ru Nanocatalysts Prepared by Chemical Reduction of RuCl3 and Thermal Decomposition of Ru3(CO)12 in the Sunlight-Powered Sabatier Reaction

The preparation of Ru nanoparticles supported on γ-Al2O3 followed by chemical reduction using RuCl3 as a precursor is demonstrated, and their properties are compared to Ru nanoparticles supported on γ-Al2O3 prepared by impregnation of γ-Al2O3 with Ru3(CO)12 and subsequent thermal decomposition. The Ru nanoparticles resulting from chemical reduction of RuCl3 are slightly larger (1.2 vs. 0.8 nm). In addition, Ru nanoparticles were deposited on Stöber SiO2 using both deposition techniques. These particles were larger than the ones deposited on γ-Al2O3 (2.5 and 3.4 nm for chemical reduction and thermal decomposition, respectively). Taking into account the size differences between the Ru nanoparticles, all catalysts display similar activity (0.14–0.63 mol·gRu−1·h−1) and selectivity (≥99%) in the sunlight-powered Sabatier reaction. Ergo, the use of toxic and volatile Ru3(CO)12 can be avoided, since catalysts prepared by chemical reduction of RuCl3 display similar catalytic performance

Safety and Efficacy of Nivolumab Monotherapy in Recurrent or Metastatic Cervical, Vaginal, or Vulvar Carcinoma: Results From the Phase I/II CheckMate 358 Trial

Purpose: Nivolumab was assessed in patients with virus-associated tumors in the phase I/II CheckMate 358 trial (ClinicalTrials.gov identifier: NCT02488759). We report on patients with recurrent/metastatic cervical, vaginal, or vulvar cancers. Patients and methods: Patients received nivolumab 240 mg every 2 weeks. Although patients with unknown human papillomavirus status were enrolled, patients known to have human papillomavirus-negative tumors were ineligible. The primary end point was objective response rate. Duration of response (DOR), progression-free survival, and overall survival were secondary end points. Safety and patient-reported outcomes were exploratory end points. Results: Twenty-four patients (cervical, n = 19; vaginal/vulvar, n = 5) were enrolled. Most patients had received prior systemic therapy for metastatic disease (cervical, 78.9%; vaginal/vulvar, 80.0%). Objective response rates were 26.3% (95% CI, 9.1 to 51.2) for cervical cancer and 20.0% (95% CI, 0.5 to 71.6) for vaginal/vulvar cancers. At a median follow-up of 19.2 months, median DOR was not reached (range, 23.3 to 29.5+ months; + indicates a censored observation) in the five responding patients in the cervical cohort; the DOR was 5.0 months in the single responding patient in the vaginal/vulvar cohort. Median overall survival was 21.9 months (95% CI, 15.1 months to not reached) among patients with cervical cancer. Any-grade treatment-related adverse events were reported in 12 of 19 patients (63.2%) in the cervical cohort and all five patients in the vaginal/vulvar cohort; there were no treatment-related deaths. In the cervical cohort, nivolumab treatment generally resulted in stabilization of patient-reported outcomes associated with health status and health-related quality of life. Conclusion: The efficacy of nivolumab in patients with recurrent/metastatic cervical and vaginal or vulvar cancers is promising and warrants additional investigation. No new safety signals were identified with nivolumab treatment in this population

Measuring children’s involvement as an indicator of curriculum effectiveness : a curriculum evaluation of a selected child study centre in Singapore

This paper presents one aspect of a research project evaluating a curriculum model of a selected child study centre in Singapore. An issue of worldwide interest and concern is the &lsquo;quality of learning&rsquo; debate as it relates to early childhood centres. In Singapore, the government is focusing on expansion in child care settings and increases in the amount of funded training. One of the issues surrounding prior-to-school education raises the question of how one measures the quality of teaching and learning, to describe the value of using, funding and promoting early education. The research reported in this study used a quasi experimental research paradigm to assess one aspect of the quality of a curriculum programme in a child study centre in Singapore. Children aged between 18 months and 6 years (N = 81) participated in the research. Using the observation scale of Laevers&rsquo; Child Involvement Scale, the active involvement of children in learning experiences was measured. The findings are presented and discussed