In vivo laser Doppler holography of the human retina

The eye offers a unique opportunity for non-invasive exploration of cardiovascular diseases. Optical angiography in the retina requires sensitive measurements, which hinders conventional full-field laser Doppler imaging schemes. To overcome this limitation, we used digital holography to perform laser Doppler perfusion imaging of the human retina in vivo with near-infrared light. Wideband measurements of the beat frequency spectrum of optical interferograms recorded with a 39 kHz CMOS camera are analyzed by short-time Fourier transformation. Power Doppler images and movies drawn from the zeroth moment of the power spectrum density reveal blood flows in retinal and choroidal vessels over 512 $\times$ 512 pixels covering 2.4 $\times$ 2.4 mm$^2$ on the retina with a 13 ms temporal resolution.Comment: 5 pages, 5 figure

Pulsatile microvascular blood flow imaging by short-time Fourier transform analysis of ultrafast laser holographic interferometry

We report on wide-field imaging of pulsatile microvascular blood flow in the exposed cerebral cortex of a mouse by holographic interferometry. We recorded interferograms of laser light backscattered by the tissue, beating against an off-axis reference beam with a 50 kHz framerate camera. Videos of local Doppler contrasts were rendered numerically by Fresnel transformation and short-time Fourier transform analysis. This approach enabled instantaneous imaging of pulsatile blood flow contrasts in superficial blood vessels over 256 x 256 pixels with a spatial resolution of 10 microns and a temporal resolution of 20 ms.Comment: 4 page

A Galois-Grothendieck-type correspondence for groupoid actions

In this paper we present a Galois-Grothendiecktype correspondence for groupoid actions. As an application a Galois-type correspondence is also given

On the structure of skew groupoid rings which are Azumaya

In this paper we present an intrinsic description of the structure of an Azumaya skew groupoid ring, having its center contained in the respective ground ring, in terms of suitable central Galois algebras and commutative Galois extensions

On partial Galois Azumaya extensions

Let α be a globalizable partial action of a finite group G over a unital ring R, A=R⋆αG the corresponding partial skew group ring, Rα the subring of the α-invariant elements of R and α⋆ the partial inner action of G (induced by α) on the centralizer CA(R) of R in A. In this paper we present equivalent conditions to characterize R as an α-partial Galois Azumaya extension of Rα and CA(R) as an α⋆-partial Galois extension of the center C(A) of A. In particular, we extend to the setting of partial group actions similar results due to R. Alfaro and G. Szeto [1,2,3]

A variant of the primitive element theorem for separable extensions of a commutative ring

In this article we show that any strongly separable extension of a commutative ring R can be embedded into another one having primitive element whenever every boolean localization of R modulo its Jacobson radical is von Neumann regular and locally uniform