The elastic modulus, shear modulus, and Poisson’s ratio of timber are the elastic constants characterizing its material properties. In this paper, the transient excitation method was used to ...dynamically measure the 10 elastic constants of the falling larch wood under the condition of the free board and cantilever board, that is, 3 elastic moduli E, 3 shear moduli G, and 4 Poisson’s ratios μ. The other two Poisson’s ratios μ were derived using the principle of orthogonality. At the same time, the elastic modulus, shear modulus, and Poisson’s ratio under static conditions were tested and verified by symmetrical four-point bending, asymmetrical four-point bending, and tensile methods. This study is expected to have good application value and practical significance for timber as an engineering structural material, which is widely used in architecture, decoration, furniture, transportation, musical instruments, and in other fields.
The elastic modulus, shear modulus, and Poisson's ratio of timber are the elastic constants characterizing its material properties. In this paper, the transient excitation method was used to ...dynamically measure the 10 elastic constants of the falling larch wood under the condition of the free board and cantilever board, that is, 3 elastic moduli E, 3 shear moduli G, and 4 Poisson's ratios μ. The other two Poisson's ratios μ were derived using the principle of orthogonality. At the same time, the elastic modulus, shear modulus, and Poisson's ratio under static conditions were tested and verified by symmetrical four-point bending, asymmetrical four-point bending, and tensile methods. This study is expected to have good application value and practical significance for timber as an engineering structural material, which is widely used in architecture, decoration, furniture, transportation, musical instruments, and in other fields.
The extraction of bayberry tannins has potential to maximize the utilization of a forest waste. This study employed a four-level central composite design through response surface methodology to ...optimize the extraction of tannin from bayberry barks through ultrasound-assisted extraction (UAE). The effects of solute to solvent ratio (STSR), solvent concentration (SC), extraction time (ET), and sonication temperature (ST) on the total extraction yield of total condensed tannin (TCT yield) and total phenolic content (TPC) were investigated. The extracts were characterized with matrix-assisted laser desorption-time of flight mass spectrometer (MALDI-TOF MS), nuclear magnetic resonance (NMR), and gel permeation chromatography (GPC). The optimized condition was reached when the STSR and ST were set at 1:57.16 g/mL and 71.3%, when the ET and the ST was 39.1 min and 48.75 °C. In these conditions, the TCT yield and TPC reached their maximum values of 17.55% and 365.01 mg GAE/g, respectively. Furthermore, the polyflavonoids of bayberry tannin ranged from dimers to heptamers, which were only composed of proanthocyanidins (PC) containing galloy groups.
Based on the temporal-spatial distribution features of ancient settlement sites from the middle and late Neolithic Age to the Han dynasty in the Chaohu Lake Basin of Anhui Province, East China, using ...the methods of GIS combined with the reconstructed paleoen- vironment by the records of lake sediment since Holocene, the transmutation of ancient set- tlements with response to environmental changes in this area has been discussed. Studies show that the main feature of transmutation of ancient settlements from the middle and late Neolithic Age to the Han Dynasty was that the distribution of settlements in this area changed from high altitudes to low ones and kept approaching the Chaohu Lake with the passage of time. These could be the response to the climate change from warm-moist to a relatively warm-dry condition during the middle Holocene, leading to the lake level fluctuations. The large area of exposed land provided enough space for human activities. These indicate that the above changes in geomorphologic evolution and hydrology influenced by climate condi- tions affected the transmutation of ancient settlements greatly. The distribution pattern of settlement sites was that the number of sites in the west was more than in the east. This pattern may be related to the geomorphologic conditions such as frequent channel shifting of the Yangtze River as well as flood disasters during the Holocene optimum. Therefore, climate change was the inducement of the transmutation of ancient settlements in the Chaohu Lake Basin, which exerted great influence on the distribution, expansion and development of the ancient settlements.
Laser shock peening (LSP) is a post-treatment process that is widely used to modify the surface microstructure and mechanical properties of parts constructed by additive manufacturing (AM). In this ...study, the influence of LSP on the microstructure and fatigue behavior of Ti–6Al–4V alloy manufactured via electron beam melting (EBM), a popular method of AM, was investigated. The microstructure of the EBM sample consisted of the β phase (~6 vol%) and α lamellar phase. Grain refinement of the α phase occurred via both dislocation evolution and deformation twinning during LSP. A theoretical description of the microstructural evolution, particularly the distribution of deformation twins, was developed. The fatigue strength and micro-hardness of the EBM samples increased by approximately 17% and 11% after LSP treatment, respectively. The fatigue fracture morphologies at three defined damage stages (crack initiation, crack propagation, and instantaneous rupture) were examined for EBM samples before and after LSP. The dominant mechanism of fatigue strength enhancement by LSP was discussed. The effects of residual compressive stress assistant with adiabatic temperature increase and grain refinement of the α phase produced by LSP reduced the pre-existing crack size, suppressed crack initiation, and increased the required work for fatigue fracture.
•The effects of LSP on the fatigue behavior of EBM Ti–6Al–4V alloy was investigated.•Microstructure evolution of EBM Ti–6Al–4V alloy by LSP treatment was discussed.•The grain refinement mechanism of EBM Ti–6Al–4V alloy by LSP was illustrated.•The dominant mechanism of fatigue strength enhancement via LSP was revealed.
Radioluminescent materials (scintillators) are widely applied in medical imaging, nondestructive testing, security inspection, nuclear and radiation industries, and scientific research. Recently, ...all‐inorganic lead halide perovskite nanocrystal (NC) scintillators have attracted great attention due to their facile solution processability and ultrasensitive X‐ray detection, which allows for large area and flexible X‐ray imaging. However, the light yield of these perovskite NCs is relatively low because of the strong self‐absorption that reduces the light out‐coupling efficiency. Here, NCs with self‐trapped excitons emission are demonstrated to be sensitive, reabsorption‐free scintillators. Highly luminescent and stable Cs3Cu2I5 NCs with a photoluminescence quantum yields of 73.7%, which is a new record for blue emission lead‐free perovskite or perovskite‐like NCs, is produced with the assistance of InI3. The PL peak of the Cs3Cu2I5 NCs locates at 445 nm that matches with the response peak of a silicon photomultiplier. Thus, Cs3Cu2I5 NCs are demonstrated as efficient scintillators with zero self‐absorption and extremely high light yield (≈79 279 photons per MeV). Both Cs3Cu2I5 NC colloidal solution and film exhibit strong radioluminescence under X‐ray irradiation. The potential application of Cs3Cu2I5 NCs as reabsorption‐free, low cost, large area, and flexible scintillators is demonstrated by a prototype X‐ray imaging with a high spatial resolution.
Nanocrystals (NCs) with self‐trapped excitons emission are demonstrated to be sensitive, reabsorption‐free scintillators. Highly blue‐emissive and stable Cs3Cu2I5 NCs with a photoluminescence quantum yield of 73.7% are produced. These Cs3Cu2I5 NCs show a strong and reabsorption‐free radioluminescence under X‐ray irradiation with an extremely high light yield, which makes them promising scintillators for low cost, large area, and flexible X‐ray imaging.
This work characterizes microstructural evolutions of electron beam melted (EBM) Ti-6Al-4V alloy modified via laser shock peening (LSP). The depth stress distribution and tensile properties of EBM ...Ti-6Al-4V alloy were measured before and after LSP. The results indicate that microstructure consists of β phase with 7.2% ± 0.4% vol.% and balance α lamellar in EBM sample, and the α lamella was refined into nano-equiaxed grains and submicro-equiaxed grains after LSP. The dominant refinement mechanism is revealed during LSP. Stacking faults were found in the LSP-treated sample, and their corresponding planes were determined as (0001) basal plane, (101¯0) prismatic plane, and (101¯1¯) pyramidal plane obtained by high resolution transmission electron microscopy. The subgrains and high-angle grains formed during dynamic recrystallization were identified by selected area electron diffraction pattern. The LSP treatment produces a significantly residual compressive stress approximately -380 MPa with the depth of compressive stress layer reaching 450 μm. Strength and elongation of the EBM sample were significantly increased after LSP. The strength and ductility enhancements are attributed to compressive stress, grain refinement and grain gradient distribution of α phase.
Background
Tuberculous meningitis (TBM) is one of the most life-threatening infectious diseases. We performed a systematic review and meta-analysis of the clinical features, outcomes, and prognostic ...factors for TBM in adults.
Methods
PubMed, EMBASE, Cochrane CENTRAL, and Web of Science were searched for studies that reported the clinical outcomes and/or risk factors for death in adults with TBM between January 1990 and July 2018. A random-effects meta-analysis model was used to pool data on clinical features, outcomes, and risk factors for death.
Results
Thirty-two studies that examined 5023 adults who had TBM met the inclusion criteria. Overall, the mortality was 22.8% 95% confidence interval (CI) 18.9–26.8 and the risk of neurological sequelae was 28.7% (95% CI 22.8–35.1). The major risk factors for death (OR > 2 and
P
< 0.05) were advanced stage of disease (OR = 6.06, 95% CI 4.31–8.53), hydrocephalus (OR = 5.27, 95% CI 2.25–12.37), altered consciousness (OR 3.33, 95% CI 1.51–7.36), altered sensorium (OR 3.31, 95% CI 2.20–4.98), advanced age (> 60 years; OR = 2.64, 95% CI 1.27–5.51), and cerebral infarction (OR = 2.35, 95% CI 1.63–3.38). The clinical features and diagnostic findings present in more than four-fifths of the patients were fever (86.3%, 95% CI 82.4–89.8) and low CSF/serum glucose ratio (80.6%, 95% CI 64.8–92.6).
Conclusions
Adults with TBM have high rates of mortality. Clinicians should maintain a high clinical suspicion for patients who present with certain clinical features, and should pay more attention to prognostic factors.
Carbon quantum dots co-doped with iron and nitrogen (Fe@NCDs) were synthesized by using
Passiflora edulis Sims
(
P. edulis
) as a precursor. The Fe@NCDs exhibit outstanding peroxidase-mimetic ...activity owing to successful doping with iron resulting in a behavior similar to that of iron porphyrins. In the presence of H
2
O
2
, the Fe@NCDs catalyze the oxidation of the peroxidase substrate 3,3′,5,5′-tetramethylbenzidine (TMB) with a color change from colorless to blue. The blue oxidation product has a characteristic absorption peaking at 652 nm. A colorimetric assay was worked out for uric acid (UA) that measures the hydrogen peroxide produced during oxidation of UA by uricase. Response is linear in the 2–150 μM UA concentration range, and the limit of detection is 0.64 μM. The method was applied to the determination of UA in (spiked) urine, and recoveries ranged from 92.0 to 103.4%.
Graphical abstract
Schematic representation of the fabrication of iron and nitrogen co-doped carbon dots (Fe@NCDs) using
Passiflora edulis Sims
as carbon-based materials. First, uric acid (UA) was oxidized to generate H
2
O
2
by uricase. Then, the Fe@NCDs catalyzed the oxidation of 3,3′,5,5′-tetramethylbenzidine (TMB) to form blue-colored oxidized TMB (oxTMB) in the presence of H
2
O
2
. UA can be quantified based on the theory.
Occupational and environmental Sb exposure has been associated with increased risk of respiratory diseases and lung cancer, but the toxicities and molecular mechanisms of Sb have been less ...investigated. In the present study, we first analyzed the Sb toxicity profile of lung adenocarcinoma A549 cells, and found that Sb dose-dependently decreased the cell viability and arrested cell cycle at G2/M but did not induce apoptosis. We next investigated the role of reactive oxygen species (ROS) involved in Sb-induced cytotoxicity. The results showed that Sb did not significantly induce cytosolic ROS production by NADPH oxidase (NOX) and the NOX inhibitors did not ameliorate the Sb-induced cell viability loss in A549 cells. However, the level of mitochondrial ROS (mtROS) was significantly increased in Sb-exposed cells and the mitochondria-targeted antioxidant significantly improved cell viability. These results suggested that mitochondria but not NOX is the major source of ROS production and mtROS plays a critical role in Sb-induced cytotoxicity. Furthermore, we found that Sb induced mitochondria dysfunction including the significant decrease of ATP level and mitochondrial membrane potential. Finally, Sb exposure decreased the activity of complex I and complex III, the level of -SH and GSH in mitochondria, and the activity of mitochondrial GR, GPx and TrxR, but increased the mitochondrial SOD activity, suggesting the disruption of mitochondrial redox homeostasis. Taken together, these findings suggested that Sb impaired mitochondrial redox homeostasis, resulting in formation of mtROS, thereby inhibited mitochondrial function and led to cytotoxicity.
Display omitted
•Sb exposure dose-dependently decreases the cell viability through oxidative stress.•Mitochondria but not NADPH oxidase was the major source of ROS production by Sb exposure.•Sb inhibited the activity of respiratory complex III and abolished the thiol-containing antioxidants in mitochondria.•Sb-induced the disruption of mitochondrial redox homeostasis resulted in mitochondrial dysfunction and cytotoxicity.
PDF
