Cavity Density Research Articles

Fine-scale habitat utilization by birds in an ancient oak (Quercus spp.) wood-pasture in southwestern Turkey

Wood-pastures are disappearing rapidly in the eastern Mediterranean basin due to changes in land use. Traditional farming by means of goat husbandry and pollarding has allowed many trees to become old, creating valuable habitats for biodiversity. Developing viable management schemes for habitats of conservation concern require studies aiming at identifying relationships between habitat structure and associated species. In this study, the associations between habitat structure and bird species diversity were studied on a fine scale, using data obtained from transect inventories in an oak wood-pasture in southwestern Turkey. Almost all species were most abundant where trunk size, basal area or tree density peaked. Diversity of ground-nesters was slightly and positively associated with an increase in basal area. Low canopy-nesters were positively associated with an increase in shrub density, whereas there was a negative association for high canopy-nesters. Secondary cavity-nesters were unrelated to the density of small trunk cavities but exhibited a positive association with basal area of trees. Contrarily, primary cavity-nesters preferred trees with larger cavities, although this was most likely due to the presence of other desirable attributes of the very same trees. The results of this study give important insights to the structural and spatial organization of bird assemblages in a little studied but rich, culturally managed ecosystem in the Mediterranean.

Habitat-mediated breeding performance of Lewis's Woodpeckers (Melanerpes lewis) in British Columbia.

Tree cavities provide a critical resource for cavity-nesting animals, and high quality cavities can be difficult for animals to acquire in habitats where competition is high. We investigated the breeding performance of Lewis’s Woodpeckers in three habitat types in British Columbia, Canada in 2013 and 2014. We also assessed whether the number of nest competitors and cavity availability influenced the habitat specific breeding performance of this threatened cavity nesting species. We found that daily nest survival rate was lower in burned habitat (0.15 ± 0.08 (0.05–0.37)) than in live pine (0.72 ± 0.10 (0.51–0.87)) or cottonwood (0.69 ± 0.09 (0.51–0.83)) habitats. However, hatching success (the proportion of eggs that hatch) was lower in live pine habitat (0.59 ± 0.09 95% CI) than burned (0.77 ± 0.19 95% CI) or cottonwood (0.80 ± 0.07 95% CI) habitat, and the fledging success of successful nests in live pine and burned habitat (1.86 ± 0.31 and 1.88 ± 0.59 95% CI, respectively) was slightly lower than in cottonwood habitat (2.61 ± 0.45 95% CI). Consequently, Lewis’s Woodpeckers in cottonwood habitat produced more fledglings per nesting attempt (2.05 ± 0.49 95% CI) than in live pine (1.53 ± 0.35 95% CI) or burned (0.79 ± 0.49 95% CI) habitat. Habitats differed in the number of nesting competitors and the number of suitable cavities surrounding active Lewis’s Woodpecker nests. Our results showed that cavity density best explained breeding performance differences although the mechanisms remain unclear. There was no evidence that the number of heterospecific nest competitors, including the invasive European Starling (Sturnus vulgaris), explained or influenced Lewis’s Woodpecker breeding performance. Cavity density influenced the productivity of successful nests but did not explain habitat differences in hatching success or daily nest survival. Further work is required to understand the mechanistic basis for the habitat specific breeding performance of Lewis’s Woodpeckers. Habitat differences in breeding performance in British Columbia are not consistent with those in other regions, highlighting the importance of regionally-specific demographic data for managing species at risk.

Characterization of ion irradiated microstructure and cavity swelling evolution up to high doses in austenitic stainless steels representative of PWR internals

Ion irradiations have been performed at 450 °C on 304 and 304L austenitic stainless steels representative of PWR internals structure up to high doses (close to 100 dpa). TEM and APT have been carried out on irradiated samples. Depending on the dose, Frank loops, dislocation network, cavities, precipitates and segregations have been observed in both 304 steels grades. Their evolution with dose, and in particular for cavities and corresponding swelling, is described and potential microstructural differences between materials are highlighted. It appears that swelling is limited even up to high doses in both materials due to only slight evolution of cavity density and size from intermediate to high doses. As the irradiation temperature has been chosen to simulate PWR microstructure taking into account a temperature/flux shift effect, the microstructural results are discussed and compared with those of PWR.

Do tree cavity density and characteristics vary across topographical habitats in the tropics? A case study from Xishuangbanna, southwest China

Despite the influence of cavities on the survival and distribution of cavity-dependent fauna, the variation in the density and characteristics of tree cavities across different habitat types in tropical forests is unknown. In this study, we surveyed 26 312 living trees from 376 species and compared cavity density and characteristics (height, size, type, and orientation) across five habitat types (valley, low-slope, high-slope, high-gully, and high-plateau) in a 20-hectare tropical rainforest in southwest China. From a total of 2047 cavities, we found that cavity density was mainly driven by habitat rather than tree species richness or diameter at breast height (DBH), and the characteristics of cavities were not uniformly distributed across habitats. Cavities were significantly more abundant in high- and low-slope than high-plateau habitats. Compared with other habitats, more “butt hollow” cavity types were found in high-slope habitat and they occurred at a lower tree height, whereas more “crack” cavities were found in low-slope habitat and they had a narrower entrance diameter. Although the mean orientation of cavities faced towards the northeast, cavity orientation varied significantly across habitat types. Our results indicate that certain types of cavities are concentrated in specific habitat types, which can provide avenues for forest management and biodiversity conservation. We highlight the importance of habitat heterogeneity in providing resources for cavity nesters.

西双版纳不同森林类型的树洞密度及其特征

西双版纳不同森林类型的树洞密度及其特征

Epicoccum nigrum-induced respiratory infection in a wild Eurasian scops owl (Otus scops).

A wild adult Eurasian scops owl (Otus scops), which was unable to fly, was rescued. Physical examination revealed a sticky exudate around the glottis. Heterophilic leukocytosis was identified through complete blood count, and radiography revealed a marked elevated density of posterior air sacs and inner cavities in both sides of the humerus and femur. Fungal cultures of samples taken from the owl suggested a respiratory fungal infection. Through molecular typing, the fungus was identified as Epicoccum nigrum. The owl was treated with oral itraconazole and broad-spectrum antibiotics. After one month, the inner cavities of pneumatic bones were slightly distinguishable by radiography and the owl started to fly well. Two months later, the air sac and all pneumatic bones displayed normal appearance.

Biological Response to Recombinant Human Bone Morphogenetic Protein-2 on Bone-Implant Osseointegration in Ovariectomized Experimental Design.

The aim of this study is to investigate the effects of recombinant human bone morphogenetic protein-2 (rhBMP-2) on bone-implant osteointegration in osteoporotic rats. Thirty-six female Wistar rats were randomly divided into 3 groups: sham-operation (SHAM), ovariectomized (OVX), and ovariectomized with rhBMP-2 (OVX + rhBMP-2). The bone density of right tibia was observed with x-ray and the serum alkaline phosphatase (ALP) activity was measured preovariectomy and postovariectomy using an ALP-kit. In OVX + rhBMP-2 group, rhBMP-2 was embedded in the peri-implant area, while SHAM and OVX groups did not contain rhBMP-2. Four and eight weeks after implantation, the rats were killed and the right tibia with implants was taken by x-ray. Histologic changes were investigated by hematoxylin and eosin staining, scanning electron microscope (SEM), and energy dispersive spectrometer examinations. The serum ALP level was significantly higher in ovariectomized rats compared with that before ovariectomy (P < 0.05), while no difference was found in SHAM rats. At 12 weeks after ovariectomy, radiographic and histologic findings showed significant osteoporotic changes in proximal tibial metaphyses of OVX rats, including reduced cortical bone density and enlargement of bone marrow cavity compared with SHAM ones. The results of implantation verified new bone formation around implants in OVX + rhBMP-2 and SHAM groups, indicating favorable bone healing and osseointegration. No bone resorption was found in OVX + rhBMP-2 group, while some soft tissue was observed in bone-implant interface in SHAM group. In OVX group, there was no effective bone-implant osseointegration and mature bone formed around implants, and some implants were even lost due to chronic inflammation. The percentage of calcium and phosphorous atoms was significantly higher and the percentage of sulfur element was significantly lower in peri-implant area in OVX + rhBMP-2 and SHAM groups than that in OVX group. rhBMP-2 could enhance the osseous healing and restore bone-implant osseointegration in osteoporotic rats.

Can CT radiomic analysis in NSCLC predict histology and EGFR mutation status?

To assess the role of radiomic features in distinguishing squamous and adenocarcinoma subtypes of nonsmall cell lung cancers (NSCLC) and predict EGFR mutations.Institution Review Board-approved study included chest CT scans of 93 consecutive patients (43 men, 50 women, mean age 60 ± 11 years) with biopsy-proven squamous and adenocarcinoma lung cancers greater than 1 cm. All cancers were evaluated for epidermal growth factor receptor (EGFR) mutation. The clinical parameters such as age, sex, and smoking history and standard morphology-based CT imaging features such as target lesion longest diameter (LD), longest perpendicular diameter (LPD), density, and presence of cavity were recorded. The radiomics data was obtained using commercial CT texture analysis (CTTA) software. The CTTA was performed on a single image of the dominant lung lesion. The predictive value of clinical history, standard imaging features, and radiomics was assessed with multivariable logistic regression and receiver operating characteristic (ROC) analyses.Between adenocarcinoma and squamous cell carcinomas, ROC analysis showed significant difference in 3/11 radiomic features (entropy, normalized SD, total) [AUC 0.686–0.744, P = .006 to <.0001], 1/3 clinical features (smoking) [AUC 0.732, P = .001], and 2/3 imaging features (LD and LPD) [AUC 0.646–0658, P = .020 to .032]. ROC analysis for probability variables showed higher values for radiomics (AUC 0.800, P < .0001) than clinical (AUC 0.676, P = .017) and standard imaging (AUC 0.708, P < .0001). Between EGFR mutant and wild-type adenocarcinoma, ROC analysis showed significant difference in 2/11 radiomic features (kurtosis, K2) [AUC 0.656–0.713, P = .03 to .003], 1/3 clinical features (smoking) [AUC 0.758, P < .0001]. The combined probability variable for radiomics, clinical and imaging features was higher (AUC 0.890, P < .0001) than independent probability variables.The radiomics evaluation adds incremental value to clinical history and standard imaging features in predicting histology and EGFR mutations.

Helium irradiated cavity formation and defect energetics in Ni-based binary single-phase concentrated solid solution alloys

Binary single-phase concentrated solid solution alloys (SPCSAs), including Ni80Co20, Ni80Fe20, Ni80Cr20, Ni80Pd20, and Ni80Mn20 (in atomic percentage), were irradiated with 200 keV He+ ions at 500 °C. He cavity size and density distribution were systematically investigated using transmission electron microscope. Here we show that alloying elements have a clear impact on He cavity formation. Cavity size is the smallest in Ni80Mn20 but the largest in Ni80Co20. Alloying elements could also substantially affect cavity density profile. In-depth examination of cavities at peak damage region (∼500 nm) and at low damage region (∼300 nm) demonstrates that cavity size is depth (damage) dependent. Competition between consumption and production of vacancies and He atoms could lead to varied cavity size. Density functional theory (DFT) calculations were performed to obtain the formation and migration energies of interstitials and vacancies. Combined experimental and simulation results show that smaller energy gap between interstitial and vacancy migration energies may lead to smaller cavity size and narrower size distribution observed in Ni80Mn20, comparing with Ni80Co20. The results of this study call attention to alloying effects of specific element on cavity formation and defect energetics in SPCSAs, and could provide fundamental understanding to predict radiation effects in more complexed SPCSAs, such as high entropy alloys.

Enhanced nonlinear interaction effects in a four-mode optomechanical ring

With a perturbative treatment based on the Keldysh Green's function technique, we study the resonant enhancement of nonlinear interaction effects in a four-mode optomechanical ring. In such a system, we identify five distinct types of resonant scattering between unperturbed polariton modes, induced by the nonlinear optomechanical interaction. By computing the cavity density of states and optomechanical induced transparency signal, we find that the largest nonlinear effects are induced by a decay process involving the two phonon-like polaritons. In contrast to the conventional two-mode optomechanical system, our proposed system can exhibit prominent nonlinear features even in the regime when the single-photon coupling is much smaller than the cavity damping.

Microstructural evolution of the 21Cr32Ni model alloy under irradiation

The microstructural evolution of the 21Cr32Ni model alloy under ion irradiation is investigated. A set of bulk materials were irradiated at the Michigan Ion Beam Laboratory using single beam (5 MeV Fe++) to 1, 10 and 20 dpa at 440 °C and dual beam (5 MeV Fe++ plus energy degraded 1.95 MeV He++ ions) to 16.6 dpa at 446 °C. The average diameter and number density of the faulted loops and cavities formed under irradiation were characterized using Transmission Electron Microscopy (TEM). The behavior of faulted loop in the model alloy was also investigated in-situ using the Intermediate Voltage Electron Microscope (IVEM) at Argonne National Laboratory (ANL). Results show that the average faulted loop diameter decreases, but the faulted loop number density increases with increasing dose. In-situ experiments showed that the faulted loops become unfaulted during ion irradiation by interacting with network dislocations. Although the average faulted loop diameter after 16.6 dpa dual beam irradiation at 446 °C was found to be similar to those seen in samples irradiated with single beams to 10 and 20 dpa, the faulted loop number density was significantly higher in the dual beam irradiated sample. Moreover, the dual beam irradiated model alloy exhibits a significantly higher density of smaller cavities. It is also found that the size and density of the faulted loops and voids calculated for the dual beam irradiation of 21Cr32Ni model alloy at 446 °C are in better agreement with those measured in a sample neutron irradiated at 375 °C. Further discussion is presented in this study.

Role of inter-nanowire distance in metal nanowires on pool boiling heat transfer characteristics

Energy management in data centres is crucial where a maximum portion of energy is spent on thermal management and electronics cooling systems. It becomes very crucial when it comes to immersion cooling techniques (pool boiling mechanism) using dielectric fluids. Role of metal nanowires (Cu and Ag) with different inter-nanowire distance values were analysed for their pool boiling performance. Templates with different inter-pore distances (260 ± 20 nm, 320 ± 20 nm and 360 ± 20 nm) and diameter of 200 nm were used to deposit copper nanowires (CuNW) and silver nanowires (AgNW) over the copper substrate using electrodeposition technique. Electrodeposition conditions like voltage and time were optimised to obtain nanowires of near constant height and different surface density coverage. To investigate the role of these metal nanowires on pool boiling characteristics, a dedicated pool boiling experimental facility was fabricated and experiments were carried out using FC-72 as working fluid. As a result of experimental investigation, boiling incipience superheat was observed to reduce which is very important for electronics systems. Also, both the critical heat flux (CHF) and heat transfer coefficient (h) were found to be increased as compared to the bare copper surface. Increasing the distance between nanowires, decreases the number of nanowires per unit area and thus the surface density coverage. This increases the cavity density and cavity size of micron-scale cavities in favour of pool boiling enhancement. This also decreases the resistance to fluid flow at high heat flux values which delays the surface dryout and critical heat flux.

Evaluating the scale effects of metal nanowire coatings on the thermal performance of miniature loop heat pipe

In this work, the effect of metallic nanowire coating on the evaporator surface of miniature loop heat pipe is investigated. Copper Nanowires (CuNW) of three different diameters (∼35, ∼70 and ∼130 nm) and constant height of ∼25 µm were fabricated using electrodeposition technique on the evaporator surface. A dedicated holder was designed to fabricate nanowire coating on the interior surface of the evaporator section. These CuNW coated surfaces were characterised for their morphology, dimensions and wettability. Cavity density and cavity size of the nanowire coated surfaces were analysed using image processing technique and both were found to increase with increase in the diameter of nanowires. The micron scale cavities generated plays a vital role in generating the effective nucleation sites as well as improving the capillarity in the evaporator surface. The evaporator surface coated with CuNW was found to improve the heat transfer characteristics of miniature loop heat pipe (MLHP). As compared to the evaporator surface without any CuNW coating, an increase of nearly 2.7 times in the heat transfer coefficient values and a decrease of approximately one-third in the thermal resistance values were observed in nanowire coated surfaces. This was believed due to an increase in the area of thin-film evaporation. Enhanced characteristics of CuNW coated surfaces like improved bubble nucleation, capillarity and reduced thermal resistance made it possible to transfer a maximum heat load of 580 W with the surface temperature value of 83 °C. This paved a plausible way to employ these kinds of nanostructured surfaces in miniature loop heat pipes to cool high heat dissipating modern electronic equipment.

Laser induced surface and structural modification of germanium in liquid environments

Laser-induced surface and structural modifications of germanium (Ge) in liquid environments of deionized water and ethanol have been investigated. Single crystal Ge (100) has been exposed by KrF excimer laser at four different fluences. Scanning electron microscope analysis reveals the formation of cavities, cracks, and ripples in case of ablation in deionized water, whereas the formation of cavities, ridges, and pores is observed in case of ablation in ethanol. The distinctness, density, and size of cavities are significantly larger in deionized water as compared to ethanol. It is attributed to lower absorption coefficient of deionized water (0.2 × 10−2/mm) as compared to ethanol (1.2 × 10−2/mm) for 248 nm, and consequently, more energy deposition to Ge takes place in the case of ablation in deionized water as compared to ethanol. Fourier transform infrared spectroscopy shows the formation of C-H stretching vibration band in case of ethanol at two moderate fluences. Raman spectroscopy reveals that only G...

Physical and microclimate characteristics of Nyctophilus gouldi and Vespadelus vulturnus maternity-roost cavities

Context Tree cavities suitable to rear young are a key resource in managed landscapes to support viable populations of tree cavity-roosting bats. Little is known about the selection of cavities for maternity roosts, presumably because of the difficulty in accessing such roosts. Aims Our study investigated physical and microclimate characteristics of maternity roosts of two species, namely, Gould’s long-eared bat (Nyctophilus gouldi) and little forest bat (Vespadelus vulturnus). Methods Maternity-roost cavities were identified in a timber-production landscape in south-eastern Australia. Roost trees (V. vulturnus n=5; N. gouldi n=9) and a subsample of available cavity-bearing trees (n=16) were climbed to obtain cavity characteristics. Key results Vespadelus vulturnus used tree hollows exclusively, whereas N. gouldi used both tree hollows (n=7) and thick loose bark (n=2). No significant difference in roost-cavity characteristics was detected between the species. However, V. vulturnus selected significantly narrower cavity entrances (mean: 16±3mm) than those of the available cavities. Temperature did not differ between maternity roosts and available cavities when investigated after the maternity season. However, a V. vulturnus maternity roost occupied for 33 consecutive days was warmer than mean roost and available cavities, suggesting that long-term roost use may be influenced by the thermal property of a cavity. Conclusions Our study has provided the first detailed tree-cavity description of maternity roosts of N. gouldi and V. vulturnus. The nightly roost switching and the large variation of tree-cavity characteristics used by N. gouldi suggest that this species requires a high density of non-specific tree cavities that are large enough for colony formation, whereas preferred roost cavities for V. vulturnus are likely to be hollows comprising narrow entrances that facilitate long-term use. Implications Our results highlighted the likely importance of narrow roost entrances for V. vulturnus, presumably for predator protection, and the conservation of tree cavities large enough for colonies to congregate. The formation of such hollows is likely to take many decades. Poor silvicultural practices, land clearing and inappropriate management of veteran trees have the potential to have an impact on this hollow resource. Our study also highlighted the need to further assess the importance of cavity microclimate for maternity-roost selection in warm climates.

Nano-scale Mechanical Properties and Microstructure of Irradiated X-750 Ni-Based Superalloy

This study investigates the effect of irradiation on the mechanical properties of a Ni-based superalloy, X-750. 40 MeV Ni+ ions were used to irradiate the X-750 up to 1 dpa with and without 5000 appm helium pre-implantation at room temperature and 400 °C. Nano-indentation hardness tests were carried out at room temperature in the depth range of 200 to 1400 nm before and after irradiation. Cross-sectional TEM observations were performed on the irradiated materials to correlate the mechanical results with the microstructural evolution. The results show that helium pre-implantation enhances the irradiation-induced hardening due to generating a high density of small cavities and promoting the formation of larger Frank loops. In addition, nano-scale mechanical tests reveal that changing the subsequent Ni ion irradiation temperature from room temperature to 400 °C, leads to changing of the mechanical response from a softening behavior to an irradiation-induced hardening. The γ′ precipitates became disordered after irradiation at room temperature, whereas the γ′-phase remained ordered during irradiation at 400 °C. The softening effect of the γ′ instability outweighed the hardening impact of irradiation-induced defects such as cavities and Frank loops, leading to a hardness reduction for the room-temperature-irradiated material. Three different obstacle-hardening models were employed to assess the individual impact of each type of defect on the material’s overall strength enhancement. Furthermore, the superposition principle was used for each model to estimate the overall irradiation-induced strengthening, which is compared to the results from the nano-hardness measurements.

Formation, evolution and scaling of plasma synthetic jets

Plasma synthetic jet actuators (PSJAs), capable of producing high-velocity pulsed jets at high frequency, are well suited for high-Reynolds-number subsonic and supersonic flow control. The effects of energy deposition and actuation frequency on the formation and evolution characteristics of plasma synthetic jets (PSJs) are investigated in detail by high-speed phase-locked particle imaging velocimetry (PIV). Increasing jet intensity with energy deposition is mainly contributed by the increasing peak jet velocity ($U_{p}$), while decreasing jet intensity with actuation frequency is attributed to both the reduced cavity density (primary factor) and the shortened jet duration (secondary factor). The total energy efficiency of the considered PSJA ($O(0.01\,\%)$) reduces monotonically with increasing frequency, while the time-averaged thrust produced by the PSJA is positively proportional to both the deposition energy and the frequency. A simplified theoretical model is derived and reveals a scaling power law between the peak jet velocity and the non-dimensional deposition energy (exponent$1/3$). The propagation velocity of the vortex ring attached at the jet front shows a non-monotonic behaviour of initial sharp increase and subsequent mild decay. The peak values for both the propagation velocity and the circulation of the front vortex ring are reached approximately two exit diameters away from the exit. Finally, analysis of the time-averaged flow fields of the issuing PSJ indicates that the axial decay rate of the centreline velocity is proportional to the actuation frequency whereas it is invariant with the energy deposition. The jet spreading rate of the PSJ is found to be higher than steady jets but lower than piezoelectric synthetic jets. Similarly, the entrainment coefficients of the PSJ are found to be twice as high as the values for comparable steady jets.

The Influence of Chronic Kidney Disease on the Structural and Mechanical Properties of Canine Bone.

BackgroundChronic kidney disease (CKD) is common in companion animals. Secondary hyperparathyroidism is an inevitable consequence of the disease and may have deleterious effect on the bone; however, the information regarding CKD‐associated bone abnormalities in companion animals is scarce.Hypothesis/ObjectivesDogs with CKD have decreased bone quality compared to dogs without CKD.AnimalsNine dogs diagnosed with naturally occurring CKD for at least 6 months and 9 age‐matched controls.MethodsDogs with CKD were enrolled and compared to 9 age‐, weight‐, and sex‐matched control dogs with no evidence of CKD. Samples were assessed using light microscopy, mechanical testing, and microcomputed tomography. Variables evaluated included microstructural features such as number, size, and density of Haversian canals, resorption cavities and osteocytic lacunae, bone mineral density, porosity and Young's modulus.ResultsMedian lacunae size was significantly smaller in the CKD group compared to the control group (P = 0.001). Resorption cavity density was higher in the CKD compared to the control group (10 [8–14] vs. 7 [4–9]/mm2, respectively, P = 0.001). Overall porosity was significantly (2.3‐fold) higher in the CKD compared to the control group. There was no difference in Young's moduli between groups.Conclusions and Clinical ImportanceNaturally occurring CKD affects bone quality in dogs, but these changes are relatively mild and likely not to be manifested clinically. The duration of the disease in dogs evaluated here is short compared to cats and human patients, likely accounting for the more subtle changes in dogs compared to other species.

Selective detection of organophosphate through molecularly imprinted GERS‐active hybrid organic–inorganic materials

A selective sensing platform for the organophosphate paraoxon, a highly toxic organic pollutant, has been designed and tested on water samples. A porous hybrid organic–inorganic film, synthesised using tetraethoxysilane, 1,8‐bis(triethoxysilyl)octane and cetyltrimethylammonium bromide, has been molecularly imprinted with a structural analogue of paraoxon, the diethyl(4‐nitrobenzyl)phosphonate, to induce selective recognition. Exfoliated graphene has been incorporated into the porous matrix to provide enhancement of the Raman scattering signal. The Raman sensor has been tested on different concentrations of paraoxon in both ethanol and water/ethanol mixture. The molecular selectivity has been assessed by comparing the Raman signal enhancement of paraoxon with a similar organophosphate, the bis‐(4‐nitrophenyl) phosphate. The molecularly imprinted film has shown a fourfold increase of the paraoxon signal, when compared with the corresponding not‐imprinted. The evaluation of the density of molecular cavities into the molecularly imprinted samples (4.50 * 10−10 μmol μm−3) has allowed assuming that each molecular cavity is capable of providing a remarkable signal enhancement of 1.47 * 1012 count * μmol−1 only when recognising paraoxon. The material design has allowed coupling the sensitivity of the graphene‐mediated enhancement of Raman scattering with the selectivity of molecular imprinting into a single and potentially portable, analytical system. Copyright © 2017 John Wiley &amp; Sons, Ltd.

A quantified TEM analysis of number density of cavities formed in 316L stainless steels irradiated with energetic ions

The number density and the statistic analysis of defects, cavities and bubbles are important structural parameters in the characterization of the radiation resistant properties of nuclear materials. Transmission electron microscope (TEM) is a powerful tool for the quantitative characterization of irradiation defects. The accuracy of the quantitative characterization is based on the precise measurement of the thickness for the micro-region. The traditional thickness measurement method based on convergent beam electron diffraction (CBED) with tow-beam approximation proposed by Kelly and Allen is a classic technique. But, this technique can not directly measure the thickness of thinner sample with thickness less than 0.6 ξ g ( ξ g is the extinction distance of the diffraction beam g ⇀ ). It is limited in the experiment and post-data process for the thickness measurement of thinner samples. However, for the irradiated materials with high density of cavities or defects, the thinner sample preparation is necessary for the clear observation and precise statistic analysis of the high-density cavities or defects. Therefore, it is urgently needed to develop the TEM-based technology for the thickness measurement of thinner samples. In this work, we use irradiated 316L austenitic stainless steels as research sample. High-density cavities are formed in 316L austenitic stainless steels implanted by high-dose He and then irradiated with high-energy Fe13+ ions. Using focused ion beam (FIB) technique, TEM sample is prepared from the irradiated 316L austenitic stainless steels. To measure the thickness for the thinner micro-region of the 316L stainless steel TEM sample, we propose a new approach based on the CBED technology proposed by Kelly and Allen. Firstly, the extinction distance of specific diffraction beam is evaluated in the thicker micro-region by using Kelly and Allen methodology, and then this parameter is used to calculate the thickness of thinner micro-region of the same sample in which the CBED is recorded under the orientation as that of the thicker region. Using this approach, the density of the cavities and the irradiation swelling ratio in a thinner micro-region of the sample of 316L stainless steels obtained through FIB are quantitatively characterized by TEM. The experimental results confirm that our proposed CBED-based approach is suitable for the thickness measurement of the thinner 316L stainless steel samples with thickness about from 20 to 50 nm. Furthermore, to present the advantage of CBED-based method for thinner-region thickness measurement, we compare it with the thickness measurement method based on electron energy loss spectroscopy (EELS). The thickness measurement results by using EELS are the total thickness of the TEM samples, including the thickness of the surface amorphous layer introduced through the sample preparation. In contrast, the CBED-based method can provide the intrinsic thickness of the crystalline samples without the influence of surface amorphous layer. Finally, we discuss the experimental factors which influence the thickness measurement results of thinner samples by using our proposed experimental approach and the related optimization methods. It is envisaged that our proposed approach can be extended to the micro-region quantitative statistic analysis of different type of defects, such as dislocation loops, cavities, bubbles and stacking fault tetrahedrons in ion irradiated crystalline materials.