Black hood assisted colonoscopy for detection of colorectal polyps: a prospective randomized controlled study.

OBJECTIVE: Colonoscopy is considered as a standard method for detecting various kinds of colorectal polyps. However, conventional colonoscopy (CC) still has chances to miss some lesions. Some scholars have already reported that transparent hood assisted colonoscopy (THAC) can improve the detection rate of colorectal polyps. However, the efficacy of detection of colorectal polyps with black hood assisted colonoscopy (BHAC) is still unclear. In this study, BHAC was compared with CC for evaluating the efficacy of detection of colorectal polyps. PATIENTS AND METHODS: Between Sep 2014 and Apr 2015, 542 patients underwent CC and meanwhile 534 patients underwent BHAC were enrolled into this prospective randomized controlled study. Comparison of baseline characteristics, cecal intubation time, withdrawal time, total number of detected polyps, detection rate of polyps, location, size, morphology and pathological diagnosis of polyps between these two groups was performed. RESULTS: Cecal intubation time was significantly shorter in BHAC group than in CC group (6.31 ± 3.51 min vs. 7.05 ± 4.15 min, p = 0.002). The total number of detected polyps and detection rate of polyps were significantly higher in BHAC group than in CC group (349/65.36% vs. 264/48.71%, p = 0.004). CONCLUSIONS: Compared with CC, BHAC could significantly improve the detection rate of colorectal polyps, and cecal intubation time was significantly reduced by BHAC.

Instabilities and disorder-driven first-order transition of the vortex lattice

Transport studies in a Corbino disk suggest that the Bragg glass phase undergoes a first-order transition into a disordered solid. This transition shows sharp reentrant behavior at low fields. In contrast, in the conventional strip configuration, the phase transition is obscured by the injection of the disordered vortices through the sample edges, which results in the commonly observed vortex instabilities and smearing of the peak effect in NbSe2 crystals. These features are found to be absent in the Corbino geometry in which the circulating vortices do not cross the sample edges.

Dynamic instabilities and memory effects in vortex matter

The magnetic flux line lattice in type II superconductors serves as a useful system in which to study condensed matter flow, as its dynamic properties are tunable. Recent studies have shown a number of puzzling phenomena associated with vortex motion, including: low-frequency noise and slow voltage oscillations; a history-dependent dynamic response, and memory of the direction, amplitude duration and frequency of the previously applied current; high vortex mobility for alternating current, but no apparent vortex motion for direct currents; and strong suppression of an a.c. response by small d.c. bias. Taken together, these phenomena are incompatible with current understanding of vortex dynamics. Here we report a generic mechanism that accounts for these observations. Our model, which is derived from investigations of the current distribution across single crystals of NbSe2, is based on a competition between the injection of a disordered vortex phase at the sample edges, and the dynamic annealing of this metastable disorder by the transport current. For an alternating current, only narrow regions near the edges are in the disordered phase, while for d.c. bias, most of the sample is in the disordered phase--preventing vortex motion because of more efficient pinning. The resulting spatial dependence of the disordered vortex system serves as an active memory of the previous history.