47 research outputs found
Graph model for multiple scattering in lithium niobate on insulator integrated photonic networks
We present a graph-based model for multiple scattering of light in integrated
lithium niobate on insulator (LNOI) networks, which describes an open network
of single-mode integrated waveguides with tunable scattering at the network
nodes. We first validate the model at small scale with experimental LNOI
resonator devices and show consistent agreement between simulated and measured
spectral data. Then, the model is used to demonstrate a novel platform for
on-chip multiple scattering in large-scale optical networks up to few hundred
nodes, with tunable scattering behaviour and tailored disorder. Combining our
simple graph-based model with material properties of LNOI, this platform
creates new opportunities to control randomness in large optical networks
C-terminal diversity within the p53 family accounts for differences in DNA binding and transcriptional activity
The p53 family is known as a family of transcription factors with functions in tumor suppression and development. Whereas the central DNA-binding domain is highly conserved among the three family members p53, p63 and p73, the C-terminal domains (CTDs) are diverse and subject to alternative splicing and post-translational modification. Here we demonstrate that the CTDs strongly influence DNA binding and transcriptional activity: while p53 and the p73 isoform p73Îł have basic CTDs and form weak sequence-specific proteinâDNA complexes, the major p73 isoforms have neutral CTDs and bind DNA strongly. A basic CTD has been previously shown to enable sliding along the DNA backbone and to facilitate the search for binding sites in the complex genome. Our experiments, however, reveal that a basic CTD also reduces proteinâDNA complex stability, intranuclear mobility, promoter occupancy in vivo, target gene activation and induction of cell cycle arrest or apoptosis. A basic CTD therefore provides both positive and negative regulatory functions presumably to enable rapid switching of protein activity in response to stress. The different DNA-binding characteristics of the p53 family members could therefore reflect their predominant role in the cellular stress response (p53) or developmental processes (p73)
Selective intra-carotid blood cooling in acute ischemic stroke : a safety and feasibility study in an ovine stroke model
Selective therapeutic hypothermia (TH) showed promising preclinical results as a neuroprotective strategy in acute ischemic stroke. We aimed to assess safety and feasibility of an intracarotid cooling catheter conceived for fast and selective brain cooling during endovascular thrombectomy in an ovine stroke model.
Transient middle cerebral artery occlusion (MCAO, 3âh) was performed in 20 sheep. In the hypothermia group (nâ=â10), selective TH was initiated 20âminutes before recanalization, and was maintained for another 3âh. In the normothermia control group (nâ=â10), a standard 8 French catheter was used instead. Primary endpoints were intranasal cooling performance (feasibility) plus vessel patency assessed by digital subtraction angiography and carotid artery wall integrity (histopathology, both safety). Secondary endpoints were neurological outcome and infarct volumes.
Computed tomography perfusion demonstrated MCA territory hypoperfusion during MCAO in both groups. Intranasal temperature decreased by 1.1â°C/3.1â°C after 10/60âminutes in the TH group and 0.3â°C/0.4â°C in the normothermia group (pâ<â0.001). Carotid artery and branching vessel patency as well as carotid wall integrity was indifferent between groups. Infarct volumes (pâ=â0.74) and neurological outcome (pâ=â0.82) were similar in both groups.
Selective TH was feasible and safe. However, a larger number of subjects might be required to demonstrate efficacy
Determination of nutrient salts by automatic methods both in seawater and brackish water: the phosphate blank
9 pĂĄginas, 2 tablas, 2 figurasThe main inconvenience in determining nutrients in seawater by automatic methods is simply solved:
the preparation of a suitable blank which corrects the effect of the refractive index change on the recorded
signal. Two procedures are proposed, one physical (a simple equation to estimate the effect) and the other
chemical (removal of the dissolved phosphorus with ferric hydroxide).Support for this work came from CICYT (MAR88-0245 project) and
Conselleria de Pesca de la Xunta de GaliciaPeer reviewe
High-bandwidth thermo-optic phase shifters for lithium niobate-on-insulator photonic integrated circuits
Phase shifters are key components of large-scale photonic integrated circuits. For the lithium niobate-on-insulator (LNOI) platform, thermo-optic phase shifters (TOPS) have emerged as a more stable and compact alternative to common electro-optic phase shifters (EOPSs), which are prone to anomalous behavior and drifting at low frequencies. Here, we model and experimentally characterize the influence of geometry on the performance of metal strip TOPSs. Compared to EOPSs, a 10-fold reduction of the voltage-length product is measured and bandwidths beyond 100 kHz are demonstrated, while keeping the footprint as low as 0.04 mm2. This shows the potential of TOPSs as small-scale building blocks for stable tuning and switching in LNOI photonic circuits.ISSN:0146-9592ISSN:1539-479
On-chip quantum interference between independent lithium niobate-on-insulator photon-pair sources
Generating and interfering non-classical states of light is fundamental to optical quantum in formation science and technology. Quantum photonic integrated circuits provide one pathway to wards scalability by combining nonlinear sources of non-classical light and programmable circuits in centimeter-scale devices. The key requirements for quantum applications include efficient genera tion of indistinguishable photon-pairs and high-visibility programmable quantum interference. Here, we demonstrate a lithium niobate-on-insulator (LNOI) integrated photonic circuit that generates a two-photon path-entangled state, and a programmable interferometer for quantum interference. We generate entangled photons with ⌠2.3 Ă 108 pairs/s/mW brightness and perform quantum interference experiments on the chip with 96.8 ± 3.6 % visibility. LNOI is an emerging photonics technology that has revolutionized high-speed modulators and efficient frequency conversion. Our results provide a path towards large-scale integrated quantum photonics including efficient photon pair generation and programmable circuits for applications such as boson sampling and quantum communications
Dynamic and precise long-distance ranging using a free-running dual-comb laser
Long-distance ranging is a crucial tool for both industrial and scientific applications. Laser-based distance metrology offers unprecedented precision making it the ideal approach for many deployments. In particular, dual-comb ranging is favorable due to its inherently high precision and sampling rate. To make high-performance long-range dual-comb LiDAR more accessible by reducing both cost and complexity, here we demonstrate a fiber-based dual-comb LiDAR frontend combined with a free-running diode-pumped solid-state dual-comb laser that allows for sub-”m measurement precision while offering a theoretical ambiguity range of more than 200 km. Our system simultaneously measures distance with the role of each comb interchanged, thereby enabling Vernier-based determination of the number of ambiguity ranges. As a proof-of-principle experiment, we measure the distance to a moving target over more than 10 m with sub-”m precision and high update rate, corresponding to a relative precision of 1eâ7. For a static target at a similar distance, we achieve an instantaneous precision of 0.29 ”m with an update time of 1.50 ms. With a longer averaging time of 200 ms, we reach a precision of around 33 nm, which corresponds to a relative precision of about 3·1eâ9 with a time-of-flight-based approach.ISSN:1094-408
High-Bandwidth Lithium Niobate Electro-Optic Modulator at Visible-Near-Infrared Wavelengths
Lithium niobate on insulator is presented as a platform for active integrated photonics at visible-near-infrared wavelengths. An electro-optic modulator operating at 780 nm featuring an electrical 3-dB bandwidth of 35 GHz and a halfwave voltage of 2.82 V is demonstrated, enabling transmission of a 40 Gbit/s on-off keying signal
Graph model for multiple scattering in lithium niobate on insulator integrated photonic networks
ISSN:1094-408
Selective intra-carotid blood cooling in acute ischemic stroke: A safety and feasibility study in an ovine stroke model
Selective therapeutic hypothermia (TH) showed promising preclinical results as a neuroprotective strategy in acute
ischemic stroke. We aimed to assess safety and feasibility of an intracarotid cooling catheter conceived for fast and
selective brain cooling during endovascular thrombectomy in an ovine stroke model.
Transient middle cerebral artery occlusion (MCAO, 3 h) was performed in 20 sheep. In the hypothermia group (n Œ 10),
selective TH was initiated 20 minutes before recanalization, and was maintained for another 3 h. In the normothermia
control group (n Œ 10), a standard 8 French catheter was used instead. Primary endpoints were intranasal cooling
performance (feasibility) plus vessel patency assessed by digital subtraction angiography and carotid artery wall integrity
(histopathology, both safety). Secondary endpoints were neurological outcome and infarct volumes.
Computed tomography perfusion demonstrated MCA territory hypoperfusion during MCAO in both groups. Intranasal
temperature decreased by 1.1 C/3.1 C after 10/60 minutes in the TH group and 0.3 C/0.4 C in the normothermia
group (p < 0.001). Carotid artery and branching vessel patency as well as carotid wall integrity was indifferent between
groups. Infarct volumes (p Œ 0.74) and neurological outcome (p Œ 0.82) were similar in both groups.
Selective TH was feasible and safe. However, a larger number of subjects might be required to demonstrate efficacy