Phase noise cancellation in polarisation-maintaining fibre links.

The distribution of ultra-narrow linewidth laser radiation is an integral part of many challenging metrological applications. Changes in the optical pathlength induced by environmental disturbances compromise the stability and accuracy of optical fibre networks distributing the laser light and call for active phase noise cancellation. Here we present a laboratory scale optical (at 578 nm) fibre network featuring all polarisation maintaining fibres in a setup with low optical powers available and tracking voltage-controlled oscillators implemented. The stability and accuracy of this system reach performance levels below 1 × 10-19 after 10 000 s of averaging.

A compact ultranarrow high-power laser system for experiments with 578 nm ytterbium clock transition.

In this paper, we present the realization of a compact, high-power laser system able to excite the ytterbium clock transition at 578 nm. Starting from an external-cavity laser based on a quantum dot chip at 1156 nm with an intra-cavity electro-optic modulator, we were able to obtain up to 60 mW of visible light at 578 nm via frequency doubling. The laser is locked with a 500 kHz bandwidth to an ultra-low-expansion glass cavity stabilized at its zero coefficient of thermal expansion temperature through an original thermal insulation and correction system. This laser allowed the observation of the clock transition in fermionic (173)Yb with a <50 Hz linewidth over 5 min, limited only by a residual frequency drift of some 0.1 Hz/s.

Direct observation of coherent interorbital spin-exchange dynamics.

We report on the first direct observation of fast spin-exchange coherent oscillations between different long-lived electronic orbitals of ultracold 173Yb fermions. We measure, in a model-independent way, the strength of the exchange interaction driving this coherent process. This observation allows us to retrieve important information on the interorbital collisional properties of 173Yb atoms and paves the way to novel quantum simulations of paradigmatic models of two-orbital quantum magnetism.

An atomic clock with 10(-18) instability.

Atomic clocks have been instrumental in science and technology, leading to innovations such as global positioning, advanced communications, and tests of fundamental constant variation. Timekeeping precision at 1 part in 10(18) enables new timing applications in relativistic geodesy, enhanced Earth- and space-based navigation and telescopy, and new tests of physics beyond the standard model. Here, we describe the development and operation of two optical lattice clocks, both using spin-polarized, ultracold atomic ytterbium. A measurement comparing these systems demonstrates an unprecedented atomic clock instability of 1.6 × 10(-18) after only 7 hours of averaging.

Large-area fiber-optic gyroscope on a multiplexed fiber network.

We describe a fiber-optic gyroscope based on the Sagnac effect, realized on a multiplexed telecom fiber network. Our loop encloses an area of 20 km² and coexists with Internet data traffic. This Sagnac interferometer is capable of detecting signals that are larger than 10(-8) (rad/s)/√Hz, thus approaching ring laser gyroscopes without using a narrow-linewidth laser or sophisticated optics. The proposed gyroscope could be useful for seismic applications, opening new possibilities for this kind of optical fiber sensor.

High-accuracy measurement of atomic polarizability in an optical lattice clock.

Presently, the Stark effect contributes the largest source of uncertainty in a ytterbium optical atomic clock through blackbody radiation. By employing an ultracold, trapped atomic ensemble and high stability optical clock, we characterize the quadratic Stark effect with unprecedented precision. We report the ytterbium optical clock's sensitivity to electric fields (such as blackbody radiation) as the differential static polarizability of the ground and excited clock levels α(clock) = 36.2612(7) kHz (kV/cm)(-2). The clock's uncertainty due to room temperature blackbody radiation is reduced by an order of magnitude to 3×10(-17).

[Stents in the treatment of stenosis of the entero-urethral junction in continent diversion: case reports]. / Gli stents nel trattamento delle stenosi della giunzione entero-uretrale nelle derivazioni continenti: casi clinici.

Strictures of entero-urethral anastomosis in orthotopic neobladder and of the catheterizable conduit in continent diversion after cystectomy are seldom encountered; they are usually treated with dilation, TUR or cold incision. 3 cases that came to our observation are presented. The first was treated with TUR after neo-bladder neck stricture in orthotopic neobladder; total incontinence occurred after this procedure. The patient at present is waiting for AS800 artificial sphincter implant. The second patient had similar features. After repeat TUR a prostacoil removable stent was placed through the stricture and removed after 5 months. At 12 months from removal the patient is continent and doesn't present clinical evidence of restriction. The third patient underwent cystectomy with Indiana continent pouch. After 4 months increasing problems in self catheterization occurred due to stricture of the catheterization conduit (appendix). He was treated twice with cold incision with early recurrence of the stricture. A permanent Memotherm stent (indicated for urethral strictures) was placed inside the appendix. After one month self catheterization was started again. At a 2 months follow up there is no evidence of stricture. In our experience, even if anecdotal, we have verified that treatment of this kind of strictures with TUR can cause incontinence or expose to further recurrences. 2 of the cases presented were treated with different kind of stents; the outcome is good even if the follow up is still short. We believe that this kind of treatment can be considered in selected cases.

[Barium peritonitis: experimental study using barium sulfate and radioactive barium]. / Le peritoniti da bario: studio sperimentale con solfato di bario e con bario radioattivo.

Barium peritonites are known to be a serious complication of barium enema examinations, being accompanied by a high mortality rate. The authors made their study injecting barium and radioactive 133Ba in the peritoneum of 68 rats without causing damages to the colon, in order to verify the toxicity of barium if injected in the peritoneum, and to evaluate the various extraperitoneal locations. Moreover, they compared the alterations caused by this agent with those consequent to a similar agent, such as talcum. The results show that barium is not toxic on its own: it gives in fact origin to granulomas similar to those caused by talcum; a particular tropism for the lymphatic tissues is present as well.