The silicon photomultiplier (SIPM) is an emerging detector technology that enables both high sensitivity and high dynamic range detection of visible and near-infrared light at a fraction of the cost ...of conventional vacuum tube photomultiplier tubes (PMTs). A low-cost detection circuit is presented and the performance of a commercial SIPM is evaluated for high-speed laser scanning microscopy applications. For moderate-to-high-speed fluorescent imaging applications, the measurements and imaging results indicate that the SIPM exceeds the sensitivity of GaAsP PMTs, while providing higher dynamic range and better saturation behavior. For low speed or applications requiring large detector areas, the GaAsP PMT retains a sensitivity advantage due to large area and lower dark counts. The calculations presented show that, above a critical detection bandwidth, the SIPM sensitivity exceeds that of a GaAsP PMT.
We derive a physically realistic model for the generation of virtual transillumination, white light microscopy images using epi-fluorescence measurements from thick, unsectioned tissue. We ...demonstrate this technique by generating virtual transillumination H&E images of unsectioned human breast tissue from epi-fluorescence multiphoton microscopy data. The virtual transillumination algorithm is shown to enable improved contrast and color accuracy compared with previous color mapping methods. Finally, we present an open source implementation of the algorithm in OpenGL, enabling real-time GPU-based generation of virtual transillumination microscopy images using conventional fluorescence microscopy systems.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Conventional two-photon microscopes use photomultiplier tubes, which enable high sensitivity but can detect relatively few photons per second, forcing longer pixel integration times and limiting ...maximum imaging rates. We introduce novel detection electronics using silicon photomultipliers that greatly extend dynamic range, enabling more than an order of magnitude increased photon detection rate as compared to state-of-the-art photomultiplier tubes. We demonstrate that this capability can dramatically improve both imaging rates and signal-to-noise ratio (SNR) in two-photon microscopy using human surgical specimens. Finally, to enable wider use of more advanced detection technology, we have formed the OpenSiPM project, which aims to provide open source detector designs for high-speed two-photon and confocal microscopy.
High-speed laser scanning microscopy frequently relies on resonant scanners due to their order of magnitude increase in imaging rate compared to conventional galvanometer scanners. However, the use ...of a nonlinear scan trajectory introduces distortion that must be corrected. This manuscript derives a new algorithm based on filtered Hermite polynomial interpolation that provides the optimal shot-noise-limited SNR for a fixed number of photons and provides higher spatial accuracy than previous methods. An open-source library is presented using the Intel advanced vector instruction set (AVX) to process up to 32 samples in parallel. Using this approach, I simultaneously demonstrate lower shot noise variance, moderately higher spatial accuracy and greater than 1 gigapixel per second interpolation rate on a desktop CPU.
Background and Aims Angiogenesis is associated with neoplastic progression of Barrett’s esophagus (BE). Volumetric optical coherence tomography angiography (OCTA) visualizes subsurface ...microvasculature without exogenous contrast agents. We investigated the association of OCTA microvascular features with low-grade dysplasia (LGD) and high-grade dysplasia (HGD). Methods Fifty-two patients undergoing BE surveillance or endoscopic eradication therapies for dysplasia were imaged using volumetric OCTA and corresponding histologic diagnoses wre obtained to yield 97 data sets (nondysplastic BE NDBE, 74; LGD, 10; HGD, 13). After evaluating OCTA image quality, 54 datasets (NDBE, 35; LGD, 8; HGD, 11) from 32 patients were used to develop a training and reading protocol. The association of abnormal vessel branching and heterogeneous vessel size with LGD/HGD and a regular honeycomb vessel pattern with NDBE were investigated. Results Blinded OCTA reading of 41 OCTA datasets (NDBE, 27; LGD, 7; HGD, 7) was performed by readers with various levels of OCT/OCTA experience including 3 OCT trainees, 1 gastroenterologist, and 2 gastroenterology fellows. Among the 6 readers, OCTA features of abnormal vessel branching and heterogeneous vessel size had an overall 94% sensitivity (95% CI, 89-99) and 69% specificity (95% CI, 62-76) for differentiating LGD/HGD versus NDBE with a mean reading time of 45 seconds per data set and moderate (kappa = .58) interobserver agreement. Conclusions Volumetric en face OCTA imaging enables rapid examination of depth resolved microvascular features with near-microscopic resolution. OCTA can visualize microvascular features associated with LGD/HGD with high accuracy, which motivates new technologic advances and future studies investigating the diagnostic performance of OCTA.
We present a light scattering study using angle-resolved low coherence interferometry (a/LCI) to assess nuclear morphology and subcellular structure within MCF-7 cells at several time points after ...treatment with chemotherapeutic agents. Although the nuclear diameter and eccentricity are not observed to change, the light scattering signal reveals a change in the organization of subcellular structures that we interpret using fractal dimension (FD). The FD of subcellular structures in cells treated with paclitaxel and doxorubicin is observed to increase significantly compared with that of control cells as early as 1.5 and 3 hours after application, respectively. The FD is then found to decrease slightly at 6 hours postapplication for both agents only to increase again from 12 to 24 hours posttreatment when the observations ceased. The changes in structure appear over two time scales, suggesting that multiple mechanisms are evident in these early apoptotic stages. Indeed, quantitative image analysis of fluorescence micrographs of cells undergoing apoptosis verifies that the FD of 4',6-diamidino-2-phenylindole-stained nuclear structures does not change significantly in cells until 12 hours after treatment, whereas that of MitoTracker stained mitochondria is seen to modulate as early as 3 hours after treatment. In contrast, cells receiving an increased dose of paclitaxel that induced G(2)-M arrest, but not apoptosis, only exhibited the early change in subcellular structure but did not show the later change associated with changes in nuclear substructure. These results suggest that a/LCI may have utility in detecting early apoptotic events for both clinical and basic science applications.
► We compare prediction accuracies of Stanghellini, Penman–Monteith and Takakura evapotranspiration models with greenhouse grown tomato and bell pepper crop during fall, spring and summer growing ...seasons under pad-fan and natural ventilation with fog cooling settings. ► No statistically significant differences in prediction accuracy between the three models were found. ► Any of these models can be implemented in a greenhouse cooling strategy for naturally ventilated greenhouse equipped with fog cooling. ► Parameters such as stomatal, aerodynamics resistances and leaf area index make the model implementations more complex, however improve the prediction accuracy.
Even though several models to predict evapotranspiration (ET) of greenhouse crops have been developed, previous studies have evaluated them under fixed greenhouse conditions. It is still not clear which model is more appropriate, accurate, and best suited for applications such as inclusion in greenhouse cooling strategies for different crops, climatic conditions and greenhouse cooling settings. This study evaluated three theoretical models (Stanghellini, Penman–Monteith and Takakura) to simulate the ET of two crops (bell pepper and tomato), under two greenhouse cooling settings (natural ventilation with fog cooling and mechanical ventilation with pad and fan), and for three growing seasons (spring, summer, fall). Predictions of ET from the models were compared to measured values obtained from sap flow gauges. Inputs of internal and external crop resistances for Stanghellini and Penman–Monteith models were calibrated separately by crop and by model. Even though Stanghellini model produced the smallest deviations of the predicted ET from the measured ET, having the best overall performance under all conditions evaluated, an analysis of variance of the daily mean square errors did not show significant differences (
α
=
0.05) between the three models. This suggested that any of the three models could be used for inclusion in a greenhouse cooling climate control strategy. However, parameter adjustments such as stomatal and aerodynamic resistances, and the need of leaf area index (LAI) in the models of Penman–Monteith and Stanghellini represent a limitation for this application. The Takakura model was found to be easier to implement; however as the crop grows, careful adjustments on the height of the solarimeter used for this approach are required. Such adjustments determine the field of view of the solarimeter and play a significant role on the determination of radiation balances and the average apparent temperature of the evaporative surface.
Sixty years after its introduction, 1,5-bis(4-amidinophenoxy)pentane (Pentamidine) is still one of the most used drugs for the treatment of the first stage of Human African trypanosomiasis and other ...neglected diseases such as malaria and leishmaniasis. These protozoan infections are prevalent in the poorest world areas such as sub-saharian and developing countries, however the increasing immigration from these countries to the richest part of the world and the overlap of HIV with parasitic infections result in a growing number of cases in developed nations. A great effort has been made to develop new generations of diamidines for the treatment of these infections transmitted by insects. This review summarises the synthesis and evaluation of pentamidine analogues reported in the last years in the effort to find new drugs with better pharmaceutical activity, higher lipophilicity and lower citotoxycicty.
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