Toward Constraintless Time-Correlated Single-Photon Counting Measurements: A New Method to Remove Pile-up Distortion

Time-Correlated Single-Photon Counting (TCSPC) is a well-renowned technique allowing to reconstruct light signals with high sensitivity and resolution. Nevertheless, to this day, its use in applications requiring a fast analysis of the sample is limited due to its long acquisition time. The reason is twofold: on one hand, it is based on a statistical method thus requiring the collection of a large number of events to properly reconstruct the signal waveform; on the other hand, the average number of photons impinging on the sensor has to be kept particularly low to avoid artifacts. Indeed, the existence of dead time of both single-photon detectors and electronics can lead to distortion in the reconstructed waveform, which can be mitigated only if the count rate is kept below few percent of the excitation frequency. Recently, it has been demonstrated that an appropriate tuning of detector dead time allows to remove such power restriction, but, unfortunately, this constraint also sets a limit to the maximum count rate of the detector. In this paper, we present a novel method for TCSPC measurements, which ensures negligible distortion at unprecedented rates without requiring any constraint on either illumination power or detector dead time. We will show that this is possible thanks to the acquisition of additional information on the status of TCSPC system. The theoretical analysis reported in this paper is supported by analytical computation and numerical simulation, taking into account also potential non idealities of a real implementation

Beyond pile-up limits: a new approach to time correlated single photon counting

The peculiar features of Time Correlated Single Photon Counting (TCSPC) have made this tool a key element in a great variety of applications, but its speed limits still prevent its exploitation in many other advanced applications. Historically, limiting the acquisition rate of a single TCSPC channel was considered the only way to avoid the so-called pile-up distortion. In this work we present a completely new approach able to remove any constraint on TCSPC while guaranteeing negligible distortion at any operating rate. This solution opens the way to the development of novel ultrafast TCSPC instrumentation

Time-Correlated Single-Photon Counting Measurements: A New Approach for High-Speed

When high timing resolution and extremely low sensitivity are needed for the analysis of optical signals, Time-Correlated Single-Photon Counting (TCSPC) is one of the preferred techniques [1]. Fluorescence Lifetime Imaging (FLIM) and single-molecule analysis are examples of applications in which these features, together with non-invasivity, are fundamental. Unfortunately, long acquisition time characterises this technique, preventing its use in many other advanced applications, where real time imaging is needed. To make the situation even worse, there is an ultimate limit on the excitation rate, which is imposed by the so called classic pile-up. Indeed, in a TCSPC measurement, it is the major source of distortion, since it allows the system to record only first impinging photons, losing the subsequent; for this reason the count rate of each acquisition channel is kept between 1%-5% of the laser repetition rate

Effect of whole linseed addition on meat production and quality of Italian Simmental and Holstein young bulls

The effect of long term dietary linseed addition on performance, carcass characteristics and meat quality of Italian Simmental (IS) and Italian Holstein (HI) young bulls was investigated. Thirty-two animals were assigned to 4 groups following a factorial design: 2 breeds - IS and IH - 7 2 diets - containing whole ground linseed (5-8% of DM) and control. IS had greater in vivo performance and carcass characteristics than IH. IS muscle had lower C14:0, C16:0, SFA, higher C18:2n-6 cis, PUFAn-6, PUFA and PUFA/SFA proportion than IH in phospholipids (PL) fraction. Linseed inclusion did not affect animal's performance and carcass characteristics. In muscle PL, linseed increased C20:0, C22:0, C23:0, C20:5n-3 and decreased C20:4n-6, PUFAn-6/n-3, PUFAn-6 concentration. Linseed decreased C14:0, C16:0 proportion in neutral lipids (NL) and increased total PUFAn-3, C18:3n-3 proportions both in NL and PL fraction. However, these differences were relatively low from a quantitative point of view

Fatty Acid Profiles of Cow’s Milk and Cheese as Affected by Mountain Pasture Type and Concentrate Supplementation

The aim of this trial was to assess the effect of pasture type and concentrate supplementation on the fatty acids (FA) composition of milk and cheese obtained during summer grazing on mountain pasture. Seventy-two Italian Simmental dairy cows were assigned to two groups that differed by the amount of concentrate supplementation: 3.0 kg/head/d (HIGH) vs. 1.5 kg/head/d (LOW). The dairy cows grazed on a Poion alpinae alliance pasture (PAST1), and subsequently they grazed on a Seslerion caeruleae alliance pasture (PAST2) for 10 d each. In the last three days of each experimental period, milk samples were collected immediately before each cheese-making event. Cheese samples were collected from each cheese loaf after 60 d of ripening. LOW showed higher isoFA, FA intermediates of the ruminal biohydrogenation, C18:3 c9,c12,c15, and total polyunsaturated fatty acid (PUFA) levels than HIGH. The pasture type had a more limited effect on FA composition of milk than concentrate level and was mainly related to monounsaturated fatty acids (MUFA), which were higher in PAST1 than PAST2 (p < 0.05). In cheeses, these differences were reduced. The phytanic acid and phytanic isomer ratio (SRR/RRR) in milk were not affected either by supplement level (p > 0.05) or by type of pasture (p > 0.05). Increasing the concentrate offered to dairy cows from 1.5 to 3.0 kg/d did not markedly influence the level of PUFA in cheeses produced during summer grazing on high mountain pasture

Efficacy of a multiple-component and multifactorial personalized fall prevention program in a mixed population of community-dwelling older adults with stroke, Parkinson's Disease, or frailty compared to usual care: The PRE.C.I.S.A. randomized controlled trial

Fall risk in the elderly is a major public health issue due to the injury-related consequences and the risk of associated long-term disability. However, delivering preventive interventions in usual clinical practice still represents a challenge