Higher-order mode suppression in twisted single-ring hollow-core photonic crystal fibers.

A hollow-core single-ring photonic crystal fiber (SR-PCF) consists of a ring of capillaries arranged around a central hollow core. Spinning the preform during drawing introduces a continuous helical twist, offering a novel means of controlling the modal properties of hollow-core SR-PCF. For example, twisting geometrically increases the effective axial propagation constant of the LP01-like modes of the capillaries, providing a means of optimizing the suppression of HOMs, which occurs when the LP11-like core mode phase-matches to the LP01-like modes of the surrounding capillaries. (In a straight fiber, optimum suppression occurs for a capillary-to-core diameter ratio d/D=0.682.) Twisting also introduces circular birefringence (to be studied in a future Letter) and has a remarkable effect on the transverse intensity profiles of the higher-order core modes, forcing the two-lobed LP11-like mode in the untwisted fiber to become three-fold symmetric in the twisted case. These phenomena are explored by means of extensive numerical modeling, an analytical model, and a series of experiments. Prism-assisted side-coupling is used to measure the losses, refractive indices, and near-field patterns of individual fiber modes in both the straight and twisted cases.

Remission from substance use disorders: A systematic review and meta-analysis.

OBJECTIVE: This paper presents a systematic review and meta-analysis of available evidence on remission rates for substance use disorders (SUDs), providing weighted mean estimates of SUD remission rates. The review also explores study-level characteristics that may explain variations in remission rates across studies. METHODS: A comprehensive search strategy identified studies published between 2000 and 2015 with follow-up periods of at least three years or reported lifetime remission outcomes for potential inclusion in the review. Remission was defined as not meeting diagnostic criteria for abuse or dependence for a minimum period of six months, as of final follow-up. A single-group summary meta-analysis was performed. Pooled estimated annual remission rates (PEARRs) were calculated. Meta-regression techniques and subgroup analyses were used to explore the association between study remission rates and key selected variables. RESULTS: Of 8855 studies identified, 21 met the eligibility criteria. The results suggested that 35.0% to 54.4% of individuals with SUDs achieved remission, and this occurred after a mean follow-up period of 17 years. The PEARRs projected few cases of SUD remission, between 6.8% and 9.1% in any given year. Studies that reported higher remission rates had longer follow-up periods, and lower sample retention rates. CONCLUSIONS: Results support the contention that SUDs are more likely to be "chronic" or long term disorders than acute disorders for a substantial number of individuals. However, more longitudinal research is required. Treatment geared to chronicity, such as assertive community treatment and intensive case management, needs to be more readily available for SUD populations.

Revealing the dark side of a bright exciton-polariton condensate.

Condensation of bosons causes spectacular phenomena such as superfluidity or superconductivity. Understanding the nature of the condensed particles is crucial for active control of such quantum phases. Fascinating possibilities emerge from condensates of light-matter-coupled excitations, such as exciton-polaritons, photons hybridized with hydrogen-like bound electron-hole pairs. So far, only the photon component has been resolved, while even the mere existence of excitons in the condensed regime has been challenged. Here we trace the matter component of polariton condensates by monitoring intra-excitonic terahertz transitions. We study how a reservoir of optically dark excitons forms and feeds the degenerate state. Unlike atomic gases, the atom-like transition in excitons is dramatically renormalized on macroscopic ground state population. Our results establish fundamental differences between polariton condensation and photon lasing and open possibilities for coherent control of condensates.

Non-thermal separation of electronic and structural orders in a persisting charge density wave.

The simultaneous ordering of different degrees of freedom in complex materials undergoing spontaneous symmetry-breaking transitions often involves intricate couplings that have remained elusive in phenomena as wide ranging as stripe formation, unconventional superconductivity or colossal magnetoresistance. Ultrafast optical, X-ray and electron pulses can elucidate the microscopic interplay between these orders by probing the electronic and lattice dynamics separately, but a simultaneous direct observation of multiple orders on the femtosecond scale has been challenging. Here we show that ultrabroadband terahertz pulses can simultaneously trace the ultrafast evolution of coexisting lattice and electronic orders. For the example of a charge density wave (CDW) in 1T-TiSe2, we demonstrate that two components of the CDW order parameter--excitonic correlations and a periodic lattice distortion (PLD)--respond very differently to 12-fs optical excitation. Even when the excitonic order of the CDW is quenched, the PLD can persist in a coherently excited state. This observation proves that excitonic correlations are not the sole driving force of the CDW transition in 1T-TiSe2, and exemplifies the sort of profound insight that disentangling strongly coupled components of order parameters in the time domain may provide for the understanding of a broad class of phase transitions.

Volume-dependent parameters in essential hypertension.

Blood pressure, renal blood flow, total blood volume (TBV), plasma renin activity, and vascular reactivities to angiotensin and norepinephrine were studied in 48 normotensive subjects and 106 essential, sustained, hypertensive patients with normal renal function, balanced sodium intake, and urinary output. A significant negative pressure-volume relationship was observed in normal subjects. Among the hypertensive patients, some were inside the 95% confidence limits of the normal curve and the others were above, indicating a disturbance in the pressure-volume relationship. A quantitative evaluation of the pressure-volume disturbance was proposed and discussed. The blood pressure of each hypertensive patient corresponded to two different blood volume values: the renal valve and the theoretical value extrapolated from the normal curve. The difference between the two values was called deltaTBV and was positive in hypertensive patients. The deltaTBV value was negatively correlated with the renal blood flow, the creatinine clearance, the plasma renin activity, and the vascular reactivities to angiotensin and norepinephrine (P less than 0.0001). The parameters were not correlated with the real blood volume. This study demonstrates quantitatively a pressure-volume disturbance in essential hypertension. This disturbance is strongly correlated with the renal function and the renin-angiotensin system changes.