Regulation of dielectric and microwave absorption properties of needle-punched polyimide/carbon fiber nonwoven composites in X-band

The application of nonwoven fabrics in the field of microwave absorption is becoming more and more extensive because of its advantages of light weight, short manufacturing process and strong designability. In this article, polyimide and carbon fiber (PI/CF) nonwoven fabrics were prepared by needle punching process, and then they were immersed in water-based polyurethane (WPU) solution containing different contents of short carbon fiber (SCF, 0–3 mm) to prepare a series of PI/CF/WPU composites. As could be seen from the microscopic morphology that the materials were well impregnated by WPU, and the prepared composites had dense structures. The tensile strength and elongation at break of pure WPU were 13.4 MPa and 161.9%, respectively. The addition of 2 wt.% SCFs in WPU increased the tensile strength to 14.4 MPa by 7.4%, while the addition of 5 wt.% SCFs decreased the tensile strength by 8.2%. Adding 2 wt.% and 5 wt.% SCFs to WPU had little effect on improving the dielectric of pure WPU. But when the PI/CF nonwoven fabrics were added, the dielectric properties of the material greatly improved. The real and imaginary parts of the PI/CF/WPU were 20.2 and 9.5 at 8.2 GHz without SCF addition, 30.4 and 15.7 with 2 wt.% SCFs addition, and 47.2 and 182.8 with 5 wt.% SCFs addition. For PI/CF/WPU without SCF, the reflectivity in the entire X-band was lower than −10 dB in the thickness of 2–2.2 mm. When the thickness was 2.2 mm, the reflectivity reached the minimum value of −25 dB at 12.4 GHz

Research on the surface subsidence monitoring technology based on fiber Bragg grating sensing

Abstract In order to monitor the process of surface subsidence caused by mining in real time, we reported two types of fiber Bragg grating (FBG) based sensors. The principles of the FBG-based displacement sensor and the FBG-based micro-seismic sensor were described. The surface subsidence monitoring system based on the FBG sensing technology was designed. Some factual application of using these FBG-based sensors for subsidence monitoring in iron mines was presented

Expression of Vesicular Glutamate Transporter 2 (vGluT2) on Large Dense-Core Vesicles within GnRH Neuroterminals of Aging Female Rats

<div><p>The pulsatile release of GnRH is crucial for normal reproductive physiology across the life cycle, a process that is regulated by hypothalamic neurotransmitters. GnRH terminals co-express the vesicular glutamate transporter 2 (vGluT2) as a marker of a glutamatergic phenotype. The current study sought to elucidate the relationship between glutamate and GnRH nerve terminals in the median eminence—the site of GnRH release into the portal capillary vasculature. We also determined whether this co-expression may change during reproductive senescence, and if steroid hormones, which affect responsiveness of GnRH neurons to glutamate, may alter the co-expression pattern. Female Sprague-Dawley rats were ovariectomized at young adult, middle-aged and old ages (~4, 11, and 22 months, respectively) and treated four weeks later with sequential vehicle + vehicle (VEH + VEH), estradiol + vehicle (E₂ + VEH), or estradiol + progesterone (E₂+P₄). Rats were perfused 24 hours after the second hormone treatment. Confocal microscopy was used to determine colocalization of GnRH and vGluT2 immunofluorescence in the median eminence. Post-embedding immunogold labeling of GnRH and vGluT2, and a serial electron microscopy (EM) technique were used to determine the cellular interaction between GnRH terminals and glutamate signaling. Confocal analysis showed that GnRH and vGluT2 immunofluorescent puncta were extensively colocalized in the median eminence and that their density declined with age but was unaffected by short-term hormone treatment. EM results showed that vGluT2 immunoreactivity was extensively associated with large dense-core vesicles, suggesting a unique glutamatergic signaling pathway in GnRH terminals. Our results provide novel subcellular information about the intimate relationship between GnRH terminals and glutamate in the median eminence.</p></div

3D reconstruction of electron microscopy image showed immunogold labels of vGluT2 associated with large dense-core vesicles in a neuroterminal of a representative middle-aged VEH treated rat.

<p>(A) Lower magnification electron microscopy image was taken from the portal capillary zone of the lateral median eminence. A vGluT2 immunolabeled neuroterminal (Term, pseudocolored in light orange) was separated from the portal capillary area (pseudocolored in pink) by tanycyte endfeet (Tan, pseudocolored in green). (B) An adjacent section showed the same vGluT2 immunopositive neuroterminal from panel A in higher magnification. The 10 nm immunogold labels for vGluT2 were seen on large dense-core vesicles (arrows). (C) The terminal shown in panel A and B was 3D reconstructed from 13 images taken from a serial section ribbon. Reconstruction showed this terminal was covered by tanycyte endfeet (green). The majority of the vesicles in this terminal were large dense-core vesicles (yellow). Immunogold beads labeled for vGluT2 were individually marked in black dots and showed extensive association to large dense-core vesicles. A large mitochondria (purple) was located in the center of the terminal. BL = basal lamina, Mit = mitochondria, Tan = Tanycyte, Term = Neuroterminal. Scale bar panel A = 100 μm, B = 500 nm, C = 200 nm.</p

Confocal microscopic images show GnRH and vGluT2 co-localization in the lateral median eminence (ME).

<p>Images were scanned from a single plane of a representative middle-aged vehicle treated rat. (A) GnRH processes were labeled with FITC (green color) and are seen along the portal capillary region (Cap) in the caudal median eminence. (B) Texas Red signals (red color) representing vGluT2 were clearly seen in the pericapillary area with a similar pattern to that of GnRH. (C) A merged image showed colocalization of GnRH and vGluT2 fluorescent signal. (D) A region from panel C (framed) is shown at higher magnification. Some punctate structures were single labeled by vGluT2 (arrow head); however, considerable overlapping of GnRH and vGluT2 signals were seen in yellow (arrows). Scale bar (shown in panel C, applies to panels A-C) = 20 μm, scale bar D = 5 μm. Cap = portal capillaries,</p

Electron microscopy images show the subcellular distribution of immunoreactive vGluT2 in neural profile of a representative young VEH treated rat.

<p>Images were taken from the neuroprofile zone of the lateral median eminence, a region in which neurosecretory axons and GnRH dendrons are located. (A) Three puncta were framed and shown in higher magnification in panels B, C, and D. (B—D) The 10 nm immunogold labels for vGluT2 were seen on large dense-core vesicles (arrowheads). (E, F) Two representative adjacent sections from a series show consistent immunogold labeling of vGluT2 on large dense-core vesicles (white and black arrowheads). Glia = glial processes, Mit = mitochondria. Scale bar panel A = 2 μm, panel F (applies to B–F) = 200 nm.</p

Quantification of the density of GnRH, vGluT2 and co-expressed puncta in the pericapillary area of the median eminence of young, middle-aged, and old rats, treated with vehicle or hormones.

<p>(A) The number of GnRH puncta per 40 μm³ were calculated and showed a decrease with age from the young to the old group (P < 0.05). (B) The density of vGluT2 puncta decreased with age from the young to the MA group (P < 0.05). (C) GnRH-vGluT2 colocalized puncta did not change significantly with age although a trend was found (P = 0.054). N = 8 rats per group.</p

Serum hormones and physiological parameters were measured to evaluate treatment outcomes.

<p>Serum estradiol levels were assayed in a subset of rats in each group (N = 3–7 per group). Other parameters were measured in all rats (N = 8 per group). (A) Serum estradiol levels at all ages were significantly elevated by E₂ in both E₂ + VEH (P < 0.0001) and E₂ + P₄ (P < 0.0001) groups, compared to VEH + VEH treatment. (B) Serum progesterone concentrations were significantly altered by hormone treatment (F = 3.91, P < 0.05) with the E₂ + P₄ group higher than VEH + VEH group. (C) The diameter of the uterine horn was significantly altered by hormone treatment (F = 114.9, P < 0.0001) with both E₂ +VEH (P < 0.001) and E₂ + P₄ (P < 0.001) higher than VEH + VEH group. (D) Pituitary weight index showed a main effect of age (F = 3.47, P < 0.05) and hormone (F = 4.67, P < 0.05) with E₂ +VEH higher than VEH + VEH group. (E) Body weight was significantly altered by age (F = 4.06, P < 0.05), with the young group lighter than old group (P < 0.05). There was a significant treatment effect on body weight (F = 3.235, P < 0.05), with significantly lower weight in the E₂ + P₄ group (p < 0.05), and a trend for lower weight in the E₂ + VEH group (p = 0.08) compared to VEH + VEH control group. (F) Statistical results were summarized to show main effects of age, treatment, and age x treatment interactions. n.s. = not significant. Abbreviations: MA: middle-aged, E₂: estradiol; P₄: progesterone; VEH: vehicle treatment.</p