65,536-ary orbital angular momentum-shift keying free-space optical communication based on few-shot learning.

In an orbital angular momentum-shift keying free-space optical (OAM-SK FSO) communication system, precisely recognizing OAM superposed modes at the receiver site is crucial to improve the communication capacity. While deep learning (DL) provides an effective method for OAM demodulation, with the increase of OAM modes, the dimension explosion of OAM superstates results in unacceptable costs on training the DL model. Here, we demonstrate a few-shot-learning-based demodulator to achieve a 65,536-ary OAM-SK FSO communication system. By learning from only 256 classes of samples, the remaining 65,280 unseen classes can be predicted with an accuracy of more than 94%, which saves a large number of resources on data preparation and model training. Based on this demodulator, we first realize the single transmission of a color pixel and the single transmission of two gray scale pixels on the application of colorful-image-transmission in free space with an average error rate less than 0.023%. This work may provide a new, to the best of our knowledge, approach for big data capacity in optical communication systems.

Hemopexin alleviates cognitive dysfunction after focal cerebral ischemia-reperfusion injury in rats.

BACKGROUND: Ischemia-reperfusion (I/R) is a critical pathophysiological basis of cognitive dysfunction caused by ischemia stroke. Heme-oxygenase-1 (HO-1) is the rate-limiting enzyme for the elimination of excessive free heme by combining with hemopexin (HPX), a plasma protein that contributes to eliminating excessive free heme during ischemia stroke. This study aimed to elucidate whether HPX could alleviate cognitive dysfunction in rats subjected to cerebral I/R. METHODS: Rats were randomly divided into five groups: sham, MCAO, Vehicle, HPX and HPX + protoporphyrin IX (ZnPPIX). Cerebral I/R was induced by MCAO. Saline, vehicle, HPX and HPX + ZnPPIX were injected intracerebroventricularly at the moment after reperfusion. Morris water maze (MWM) test was used to detect the learning and cognitive function. Western blot was used to detect the expression of HO-1 in ischemic penumbra. CD31/vWF double labeling immunofluorescence was used to detect the neovascularization in the penumbra hippocampus. The structure and function of blood-brain barrier (BBB) was detected by the permeability of Evans Blue (EB), water content of the brain tissue, the Ang1/Ang2 and VE-cadherin expression. RESULTS: Our study verified that HPX improved the learning and memory capacity. Hemopexin up-regulated HO-1 protein expression, the average vessel density in the penumbra hippocampus and the VE- cadherin expression but decreased the permeability of EB, the water content of brain tissue and the ratio of Ang1/Ang2. The effects were reversed by ZnPPIX, an inhibitor of HO-1. CONCLUSION: HPX can maintain the integrity of the blood-brain barrier and alleviate cognitive dysfunction after cerebral I/R through the HO-1 pathway.

All-fiber stable orbital angular momentum beam generation and propagation.

An all-fiber scheme for stable orbital angular momentum (OAM) beam generation and propagation is proposed and demonstrated. This scheme is based on a self-designed and manufactured graded-index few mode fiber (GI-FMF) and compatible mode selection coupler (MSC). The MSC, which consists of a conventional single mode fiber (SMF) and the GI-FMF, can effectively couple the fundamental mode in the SMF to the desired OAM mode in the GI-FMF based on phase matching condition. Meanwhile, the GI-FMF breaks the degeneracy between the desired eigenmodes and neighboring vector modes, thereby allowing the preservation and propagation of the selectively excited OAM modes. As a proof-of-principle, we have implemented an all-fiber device operating in stable OAM modes with |l| = 1. The experimental results show stable propagation of OAM beams with the mode purity of ∼95% and bandwidth of 100 nm. This all fiber device could be useful for further development of wide bandwidth OAM mode division multiplexed application.

Transverse mode switchable all-fiber Brillouin laser.

A transverse mode switchable all-fiber Brillouin laser architecture is proposed. This laser architecture consists mainly of an optical switch, a set of cascaded mode selection couplers (MSCs), and a few-mode fiber ring cavity. By switching the output signal of the optical switch, specific transverse modes generated by MSCs can be coupled into the ring cavity to excite the corresponding Brillouin scattering light. Based on the Brillouin nonlinear effect, the desired mode resonant amplification is guaranteed, and a transverse mode switchable laser beam is obtained. As a proof of principle, we have implemented an all-fiber Brillouin laser with switchable output of fundamental transverse (LP01) mode and second-order transverse (LP11) mode at the wavelength of 1550 nm. The slope efficiency and linewidth for LP01 and LP11 modes are 25.1% and 4.9 kHz, 20.9% and 4.96 kHz, respectively. Additionally, the orbital angular momentum laser beam with l=+1, -1, or 0 switchable output is also demonstrated from our all-fiber Brillouin laser system. Owing to the compact all-fiber architecture, this transverse mode switchable Brillouin fiber laser is reliable during long-term operation and thus promising for many practical applications.

Hemopexin promotes angiogenesis via up-regulating HO-1 in rats after cerebral ischemia-reperfusion injury.

BACKGROUND: Ischemia-reperfusion (I/R) is a critical pathophysiological change of ischemic stroke. Heme-oxygenase-1 (HO-1) is a rate-limiting enzyme of eliminating excessive free heme by combining with hemopexin (HPX), a plasma protein contributing to alleviating infarct size due to ischemia stroke. This study was to investigate whether HPX could improve angiogenesis after cerebral ischemia-reperfusion via up-regulating HO-1. METHODS: Rats were randomly divided into five groups: sham, MCAO, MCAO + Vehicle, MCAO + HPX and MCAO + HPX + protoporphyrin IX (ZnPPIX, an HO-1 inhibitor). Cerebral I/R was induced by MCAO. Saline, vehicle, HPX and HPX + ZnPPIX were respectively given to MCAO group, MCAO + Vehicle group, MCAO + HPX group and MCAO + HPX + ZnPPIX group at the moment after reperfusion by intracerebroventricular injection. Neurological behavioral scores(NBS) was assessed at 24 h and 7d after I/R. Real-time polymerase chain reaction (RT-PCR) was used to analyze the mRNA level of HO-1. Angiogenesis in penumbra area was assessed by immunofluorescence detection at 7d after I/R. Serum endothelial nitric oxide synthase (eNOS) was assessed by enzyme linked immunosorbent assay (ELISA) at 24 h and 7d after I/R. RESULTS: Compared with sham group, the NBS and the mRNA levels of HO-1 at 24 h and 7d after I/R in MCAO group decreased notably (P < 0.05), the new vessel density in ischemia penumbra increased notably at 7d after I/R (P < 0.05), the serum eNOS level increased at 24 h and 7d after I/R (P < 0.05). MCAO group and MCAO + Vehicle group showed no significant differences (P > 0.05). In the MCAO + HPX group, compared with MCAO + Vehicle group, the NBS and the mRNA levels of HO-1 increased drastically at 24 h and 7d after I/R (P < 0.05), the new vessel density in ischemia penumbra increased significantly at 7d after I/R (P < 0.05), the serum eNOS level at 24 h and 7d after I/R ascended notably (P < 0.05). Compared with MCAO + HPX group, the NBS assessment, new vessel density and serum eNOS level decreased at corresponding time points after I/R in MCAO + HPX+ ZnPPIX group (P < 0.05). CONCLUSION: HPX can promote angiogenesis after cerebral ischemia-reperfusion injury in rats via up-regulating HO-1.

Low-crosstalk orbital angular momentum fiber coupler design.

A fiber coupler for low-crosstalk orbital angular momentum mode beam splitter is proposed with the structure of two separate and parallel microfibers. By properly setting the center-to-center distance between microfibers, the crosstalk is less than -20 dB, which means that the purity of the needed OAM mode in output port is higher than 99%. For a fixed overlapping length, high coupling efficiency (>97%) is achieved in 1545-1560 nm. The operating wavelength is tuned to the whole C-band by using the thermosensitive liquid. So the designed coupler can achieve the tunable coupling ratio over the whole C-band, which is a prospective component for the further OAM fiber system.

High spatial resolution distributed fiber strain sensor based on phase-OFDR.

A novel method to realize high spatial resolution distributed strain measurement is proposed based on phase demodulation scheme of optical frequency domain reflectometry (OFDR). Strain information can be demodulated directly by analyzing the phase change of Rayleigh backscattered light. Strain location can be obtained with high spatial resolution by cross-correlation method using a wide scanning range of tunable laser source. Based on the above scheme, breakpoint detection with 0.1 mm spatial resolution has been demonstrated, static and dynamic strain up to 100 Hz could be distributedly measured with 10 cm spatial resolution over 200 m sensing fiber, and the minimum measurable strain is about 1 µÎµ.

Optical fiber design with orbital angular momentum light purity higher than 99.9.

The purity of the synthesized orbital-angular-momentum (OAM) light in the fiber is inversely proportional to channel crosstalk level in the OAM optical fiber communication system. Here the relationship between the fiber structure and the purity is firstly demonstrated in theory. The graded-index optical fiber is proposed and designed for the OAM light propagation with the purity higher than 99.9%. 16 fiber modes (10 OAM modes) have been supported by a specific designed graded-index optical fiber with dispersion less than 35 ps/(km∙nm). Such fiber design has suppressed the intrinsic crosstalk to be lower than -30 dB, and can be potentially used for the long distance OAM optical communication system.

All-fiber mode-locked laser based on microfiber polarizer.

A novel all-fiber mode-locked fiber laser based on microfiber polarizer is proposed and demonstrated. The microfiber polarizer is composed of two pieces of microfibers that are finely manipulated to be partly overlapped. Because of the asymmetric cross section, the microfiber polarizer shows a strong birefringence that ultimately induces a high polarization-selective feature. Compared with other polarizers, the microfiber polarizer owns the merits of simpler fabrication, lower cost, broader band, and more compact size. The polarization extinction ratio of the microfiber polarizer is 26 dB, and the stable pulse sequence with the duration of 2.9 ps is generated from this microfiber polarizer based all-fiber mode-locked laser.

Hyperhomocysteinaemia, low folate concentrations and MTHFR C677T mutation in abdominal aortic aneurysm.

BACKGROUND: Homocysteine (Hcy) has been implicated in abdominal aortic aneurysm (AAA). However, the association of Hcy, vitamin B12, and folate in patients with AAA has not been studied in China. This study was conducted with the aim to evaluate the relationship of vitamin B12, folic acid, and Hcy levels in AAA. PATIENTS AND METHODS: 463 patients who had AAA were included in this study. 463 control subjects were age- and sex-matched with the patients. In all of the subjects, we evaluated total plasma levels Hcy, vitamin B12, folic acid and the distribution of the C677T methylenetetrahydrofolate reductase (MTHFR) gene mutation. RESULTS: The mean plasma Hcy levels were significantly higher in patients with AAA compared with controls (18.37 ± 6.97 vs. 12.89 ± 4.08 µmol/L, P < 0.001). The frequency of homozygous (TT) genotype in MTHFR C677T mutation was significantly higher in patients with AAA than that in control subjects (19.4 % vs. 11.9 %, P = 0.002). The fasting Hcy correlated negatively with folate (AAA: r = - 0.311, P < 0.01; CONTROL: r = - 0.348, P < 0.01). The aneurysm size was significantly greater (P < 0.001) in patients with hyperhomocysteinemia than that in patients with normal Hcy plasma levels. The size of the AAA had a linear correlation with the plasma Hcy level (r = 0.286; P< 0.001). CONCLUSIONS: Serum folate deficiency and hyperhomocysteinemia were associated with an increased risk of AAA in Northeast China. The homozygous (TT) genotype of MTHFR gene mutation may be a crucial hereditary risk factor in AAA.

Microbial-derived peptides with anti-mycobacterial potential.

Tuberculosis (TB), an airborne infectious disease caused by Mycobacterium tuberculosis, has become the leading cause of death. The subsequent emergence of multidrug-resistant, extensively drug-resistant and totally drug-resistant strains, brings an urgent need to discover novel anti-TB drugs. Among them, microbial-derived anti-mycobacterial peptides, including ribosomally synthesized and post-translationally modified peptides (RiPPs) and multimodular nonribosomal peptides (NRPs), now arise as promising candidates for TB treatment. This review presents 96 natural RiPP and NRP families from bacteria and fungi that have broad spectrum in vitro activities against non-resistant and drug-resistant mycobacteria. In addition, intracellular targets of 22 molecules are the subject of much attention. Meanwhile, chemical features of 38 families could be modified in order to improve properties. In final, structure-activity relationships suggest that the modifications of various groups, especially the peptide side chains, the amino acid moieties, the cyclic peptide skeletons, various special groups, stereochemistry and entire peptide chain length are important for increasing the potency.

Narrow linewidth single frequency microfiber laser.

A compact 2 kHz linewidth single frequency microfiber ring laser is demonstrated. Microfiber, with a diameter of 1.88 µm, which is drawn from an Er(3+)/Yb(3+) co-doped phosphate glass fiber, serves as the gain medium. By using this microfiber, a double-knot resonator with a total length of 1.75 mm is constructed. Based on this resonator, a narrow linewidth single frequency laser with output power higher than 0.95 µW is obtained at the wavelength of 1536.1 nm. The linewidth of this microfiber laser is as narrow as 2 kHz, and the side-mode-suppression ratio is higher than 38 dB.

SnSe-Coated Microfiber Resonator for All-Optical Modulation.

In this study, a tin monoselenide (SnSe)-based all-optical modulator is firstly demonstrated with high tuning efficiency, broad bandwidth, and fast response time. The SnSe nanoplates are deposited in the microfiber knot resonator (MKR) on MgF2 substrate and change its transmission spectra by the external laser irradiation. The SnSe nanoplates and the microfiber are fabricated using the liquid-phase exfoliation method and the heat-flame taper-drawing method, respectively. Due to the strong absorption and enhanced light-matter interaction of the SnSe nanoplates, the largest transmitted power tunability is approximately 0.29 dB/mW with the response time of less than 2 ms. The broad tuning bandwidth is confirmed by four external pump lights ranging from ultraviolet to near-infrared. The proposed SnSe-coated microfiber resonator holds promising potential for wide application in the fields of all-optical tuning and fiber sensors.

[Effect of RNA interference targeting mammalian target of rapamycin on the proliferation of vascular smooth muscle cell and the intimal hyperplasia].

OBJECTIVE: To construct RNA interference (RNAi) vector of mammalian target of rapamycin (mTOR) and study the effect on the proliferation of vascular smooth muscle cell (VSMC) and the intimal hyperplasia (IH). METHODS: The sequence of short hairpin RNA (shRNA) targeting mTOR was designed and synthesized by chemical method and inserted into a retroviral vector pLXIN, then the vector was packaged in PT67 cells. The efficiency of inhibition was verified by Northern blot and Western blot after transfection to VSMC. The changes of p70s 6k and 4E-BP1 were also determined. The proliferation activity of VSMC was determined by flowcytometry and MTT. Autogenous vein graft model were established in 54 rats. Three groups were divided, including gene therapy group, control group and vein graft group. The grafted veins were harvested 7 days, 14 days and 28 days after transplanting respectively. The expression of mTOR was determined by immunohistochemistry stain and Western blot. IH was also observed. The apoptotic VSMC was determined by TUNEL. RESULTS: The shRNA fragments was inserted into pLXIN vector. The shRNA vector was successfully constructed. Additionally, the vector targeting mTOR gene could efficiently decrease the mRNA and protein expression of mTOR and p70s 6k in VSMC, while the expression of 4E-BP1 increased significantly. The cell cycle of VSMC was stunned in phase G(0)/G(1). The protein expression of mTOR in vein graft was inhibited by transfection of pLXIN-shRNA targeting mTOR (P < 0.01) and the IH was also inhibited (P < 0.01), but the apoptosis of VSMC increased significantly (P < 0.01). CONCLUSION: The mTOR RNAi retroviral vector has been constructed successfully, which can significantly inhibit the proliferation of VSMC and the IH, and promote apoptosis after vein grafting.

[Inhibition of nuclear factor kappa B attenuates multiple organ injury following ruptured abdominal aortic aneurysm: an experiment with rats].

OBJECTIVE: To investigate the effect of inhibition of nuclear factor kappa B on multiple organ injury following ruptured abdominal aortic aneurysm. METHODS: Forty-five Wistar rats underwent catheterization to observe the intestinal microcirculation blood flow, and were randomly divided into 3 equal groups. Rats of the ruptured abdominal aortic aneurysm (RAAA) group underwent laparotomy and extraction of blood to cause hemorrhage shock for 1 h (hemorrhagic shock phase), by the end of this phase normal saline at the dose of 50 ml/kg was injected intravenously, after that the abdominal aorta and bilateral common iliac arteries were blocked with artery clamps for 45 min so as to cause lower torso ischemia, and then the extracted blood was reperfused. The lungs, small intestine were taken out to undergo histological examination, and examination of lung polymorphonuclear neutrophilic leukocyte (PMN) sequestration, lung wet tissues/dry (W/D) tissues ratio, and myeloperoxidase (MPO) activity. The rats of pyrrolidine dithiocarbamate (PDTC) group were perfused with PDTC, a specific inhibitor of nuclear factor kappa B (NF-kappaB), by the end of the hemorrhagic shock phase. And the rats of the sham operation group were perfused of normal saline. RT-PCR was used to detect the mRNA expression of NF-kappaB p65 and intercellular adhesion molecule (ICAM). Western blotting was used to detect the protein expression of NF-kappaB p65 and ICAM-1. Immunohistochemistry was used to detect the expression of NF-kappaB p65 and ICAM-1 in the lung and small intestine tissues. RESULTS: Histological examination showed that severe damage could be found in the lung and small intestine of the RAAA group, and damages were significantly mild in the PDTC group. Lung PMN sequestration, W/D ratio, MPO activity were significantly increased in the RAAA group and these changes were relatively mild in the PDTC group (all P < 0.01). The intestinal microcirculation blood flow was 0.25 +/- 0.04 mlxmin(-1)xg(-1) in the RAAA group, significantly less than that of the sham operation group (0.71 +/- 0.11 mlxmin(-1)xg(-1), P < 0.01), and was 0.64 +/- 0.06 mlxmin(-1)xg(-1) in the PDTC group, significantly higher than that of the RAAA group (P < 0.01). The mRNA expression of NF-kappaB p65 in the lung of the RAAA group was 0.68 +/- 0.22, significantly higher than that of the sham operation group (0.11 +/- 0.02, P < 0.01) and that of the PDTC group (0.23 +/- 0.07, P < 0.01). The mRNA expression of NF-kappaB p65 in the intestine of the RAAA group was 0.48 +/- 0.10, significantly higher than that of the sham operation group (< 0.20 +/- 0.05, P < 0.01) and that of the PDTC group (0.27 +/- 0.06, P < 0.01). The mRNA expression of ICAM-1 in the lung of the RAAA group was 0.92 +/- 0.31, significantly higher than that of the sham operation group (0.07 +/- 0.02, P < 0.01) and that of the PDTC group (0.21 +/- 0.04, P < 0.01). The mRNA expression of ICAM-1 in the intestine of the RAAA group was 0.74 +/- 0.15, significantly higher than that of the sham operation group (0.14 +/- 0.05, P < 0.01) and that of the PDTC group (0.25 +/- 0.08, P < 0.01). The protein expression of NF-kappaB p65 in the lung of the RAAA group was 1.04 +/- 0.26, significantly higher than that of the PDTC group (0.52 +/- 0.13, P < 0.01). The protein expression of NF-kappaB p65 in the intestine of the RAAA group was 1.20 +/- 0.30, significantly higher than that of the PDTC group (0.64 +/- 0.21, P < 0.01). The protein expression of ICAM-1 in the lung of the RAAA group was 0.40 +/- 0.12, significantly higher than that of the PDTC group (0.18 +/- 0.06, P < 0.01). The protein expression of ICAM-1 in the intestine of the RAAA group was 0.46 +/- 0.15, significantly higher than that of the PDTC group (0.22 +/- 0.05, P < 0.01). Immunohistochemistry showed that NF-kappaB p65 and ICAM-1 positive cells were widely distributed in the lungs and intestine of the RAAA group and were rarely distributed in the sham operation group. CONCLUSION: PDTC attenuates the multi-organ injury by inhibiting the expression of NF-kappaB p65, thus reducing the mRNA and protein expression of its downstream gene ICAM-1 gene.

[The expression of mammalian target of rapamycin and its substrates in autogenous vein graft in rats].

OBJECTIVE: To investigate the expression of mammalian target of rapamycin (mTOR) and its substrates including p70s6k and 4E-BP1 in autogenous vein graft. METHODS: Autogenous vein graft model was established in 64 Wistar rats by transplanting the right common jugular vein to infrarenal abdominal aorta. Vein graft samples were harvested 6 hours, 1 day, 3 days, 1 week, 2 weeks, 4 weeks, 6 weeks and 8 weeks after surgery. The mRNA expression of mTOR, p70s6k and 4E-BP1 were measured by RT-PCR and in situ hybridization. Western blot and immunohistochemistry methods also were used to detect the protein expression of mTOR, p70s6k and 4E-BP1. Proliferating cell nuclear antigen (PCNA) was also detected at the same time. RESULTS: The mRNA expression of mTOR and p70s6k increased soon after vein graft transplanting, rose quickly and reached the peak 3 days to 2 weeks after surgery, which recovered 6 to 8 weeks after surgery. The expression of 4E-BP1 mRNA decreased soon after surgery and reached the lowest at 1 week, then rose to the peak 4 to 6 weeks after transplantation. Protein expression of mTOR and p70s6k reached the peak 2 to 4 weeks and recovered to normal level 8 weeks after surgery, but the expression of 4E-BP1 decreased to the lowest during 1 to 2 weeks and reached the peak 4 to 6 weeks after transplanting. The positive cells mostly located in vascular smooth muscle cell (VSMC) just like PCNA. CONCLUSIONS: The expression of mTOR and its substrates were activated in vein graft soon after transplantation, which means that mTOR and its substrates might become new targets for the prevention and therapy of stenosis or obliteration after vein graft transplanting.

[The expression and significance of hypoxia-inducible factor-1 alpha and related genes in abdominal aorta aneurysm].

OBJECTIVE: To study the expression of hypoxia-inducible factor (HIF)-1alpha and related genes in abdominal aorta aneurysm (AAA) and explore the underlying pathogenesis. METHODS: Twenty-two AAA specimens were collected and 5 normal abdominal aorta tissue were used as control. Northern blot, western blot and immunohistochemistry were used to evaluated the expression of HIF-1alpha mRNA and protein product. Western blot and immunohistochemistry method were also used to determine the expression of vascular endothelial growth factor (VEGF) and caspase-3. Microvessel density (MVD) was studied by immunohistochemistry stain of CD34. RESULTS: The expression of HIF-1alpha mRNA and protein product were significantly higher in AAA than that in normal abdominal aorta (P < 0.01). The expression of VEGF and caspase-3 were also higher in AAA and both had a significantly positive relationship with HIF-1alpha expression (P < 0.01). Most of the positive cells located in VSMC and adventitia of AAA. The MVD counts were higher in AAA. CONCLUSION: HIF-1alpha may have an important role the development of AAA, which maybe obtained by regulating the expression of VEGF or caspase-3.

[Cyclic fatigue of Vita mark II machinable ceramics under Hertzian's contact].

OBJECTIVE: To investigate the cyclic fatigue modes of Vita mark II machinable ceramics under Hertzian's contact. METHODS: Hertzian's contact technique (WC spheres r = 3.18 mm) was used to investigate the cyclic fatigue of Vita mark II machinable ceramic. All specimens were fatigued by cyclic loading in moist environment, furthermore, surviving strength was examined by three point test and morphology damage observation. RESULTS: In homogeneous Vita mark II machinable ceramics, two fatigue damage modes existed after cyclic loading with spheres under moist environment, including conventional tensile-driven cone cracking (brittle mode) and shear-driven microdamage accumulation (quasi-plastic mode). The latter generated radial cracks and deeply penetrating secondary cone crack. Initial strength degradation were caused by the cone cracks, subsequent and much more deleterious loss was caused by radial cracks. CONCLUSION: Cyclic fatigue modes of Vita mark II machinable ceramics includes brittle and quasi-plastic mode.