Study on energy release characteristics of reactive material casings under explosive loading

Reactive Materials(RMs),a new material with structural and energy release characteristics under shockinduced chemical reactions,are promising in extensive applications in national defense and military fields.They can increase the lethality of warheads due to their dual functionality.This paper focuses on the energy release characteristics of RM casings prepared by alloy melting and casting process under explosive loading.Explosion experiments of RM and conventional 2A12 aluminum alloy casings were conducted in free field to capture the explosive fireballs,temperature distribution,peak overpressure of the air shock wave and the fracture morphology of fragments of reactive material(RM)warhead casings by using high-speed camera,infrared thermal imager temperature and peak overpressure testing and scanning electron microscope.Results showed that an increase of both the fireball temperature and air shock wave were observed in all RM casings compared to conventional 2A12 aluminum ally casings.The RM casings can improve the peak overpressure of the air shock wave under explosion loading,though the results are different with different charge ratios.According to the energy release characteristics of the RM,increasing the thickness of RM casings will increase the peak overpressure of the near-field air shock wave,while reducing the thickness will increase the peak overpressure of the far-field air shock wave.

Study of simple plane wave generator with an air-metal barrier

Plane wave generators(PWGs) are used to accelerate flyer plates to high velocities with their generated plane waves,which are widely used in the test of dynamic properties of materials.The traditional PWG is composed of two explosives with different detonation velocities.It is difficult to implement the related fabrication processes and control the generated waves due to its complicated structures.A simple plane wave generator is presented in this paper,which is composed of two identical cylindrical high explosive(HE) charges and an air-metal barrier.A theoretical model was established based on two different paths of the propagation of detonation waves,based on which the size of air-metal barrier was calculated for a given charge.The corresponding numerical simulations were also carried out by AUTODYN-2D based on the calculated results,which were used to compare with the theoretical calculations.A detonation wave with a flatness of 0.039 μs within the range of 70-percent diameter of the main charge was obtained through the simulations.

Experimental study on WFeNiMo high-entropy alloy projectile penetrating semi-infinite steel target

The appearance of high-entropy alloys (HEAs) makes it possible for a material to possess both high strength and high ductility. It is with great potential to apply HEAs under extreme conditions such as in the penetration process. In this paper, experiments of WFeNiMo HEA and tungsten heavy alloy (WHA) projectiles penetrating medium-carbon steel were conducted by using the ballistic gun and two-stage light-gas gun that can accelerate projectiles to impact velocities ranging from 1162 m/s to 2130 m/s. Depth of penetration (DOP) at elevated impact velocities of HEA and WHA projectiles were obtained firstly. Combined with the macroscopic and microscopic analysis of the residual projectiles, the transition of the penetration mode of the WFeNiMo HEA projectile was identified systemically. The experimental results indicated that the penetration mode of the HEA projectile changes from self-sharpening to mushrooming with the increase of impact velocity, while for the WHA projectile, the penetration mode is always mushrooming. The microstructure of the residual HEA projectiles showed that the phases tangle with each other and the morphology of the microstructure of the phases differs in the two penetration modes. Besides, the evolution of shear bands and fractures varies in the two modes. The evolution of the microstructure of HEAs causes the sharp-pointed nose to disappear and the HEA projectile ultimately becomes blunt as the impact velocity increases.

Neurocutaneous melanosis with an intracranial cystic-solid meningeal melanoma in an adult:A case report and review of literature

BACKGROUND Neurocutaneous melanosis(NCM)is a rare congenital,nonhereditary neurocutaneous syndrome that mainly occurs in children;adult NCM is very rare.Due to its rarity,the clinical features and treatment strategies for NCM remain unclear.The purpose of this study was to explore the clinical features,diagnosis,treatment and prognosis of NCM in adults.Most intracranial meningeal melanomas are solid masses,and cystic-solid malignant melanomas are very rare.Due to the lack of data,the cause of cystic changes and the effect on prognosis are unknown.CASE SUMMARY A 41-year-old woman was admitted to the hospital with intermittent headache for 1 mo.Magnetic resonance imaging(MRI)showed a 4.7 cm×3.6 cm cystic-solid mass in the left temporal lobe with peritumoral edema.The entire mass was removed,and postoperative pathology indicated malignant melanoma.CONCLUSION MRI is the first-choice imaging approach for diagnosing central nervous system diseases in NCM patients,although cerebrospinal fluid may also be used.At present,there is no optimal treatment plan;gross total resection combined with BRAF inhibitors and MEK inhibitors might be the most beneficial treatment.

INVESTIGATION OF MICROSTRUCTURE AND CONDUCTIVE MECHANISM OF HIGH DENSITY POLYETHYLENE/CARBON BLACK PARTICLE COMPOSITE BY POSITRON ANNIHILATION LIFETIME SPECTROSCOPY

The microstructure and conductive mechanism of high density polyethylene/carbon black (HDPE/CB) composite were investigated by positron annihilation lifetime spectroscopy (PALS). The PALS were measured in two series of samples, one with various CB contents in the composites and the other with various gamma-irradiation doses in HDPE/CB composite containing 20 wt% CB. It was found that CB particles distribute in the amorphous regions, the CB critical content value in HDPE/CB composite is about 16.7 wt% and the suitable gamma-irradiation dose for improving the conductive behavior of HDPE/CB composite is about 20 Mrad. The result observed for the second set of samples suggests that gamma-irradiation causes not only cross-linking in amorphous regions but also destruction of the partial crystalline structure. Therefore, a suitable irradiation dose, about 20 Mrad, can induce sufficient cross-linking in the amorphous regions without enhancing the decomposition of crystalline structure, so that the positive temperature coefficient (PTC) effect remains while the negative temperature coefficient (NTC) effect is suppressed. A new interpretation of the conductive mechanism, which might provide a more detailed explanation of the PTC effect and the NTC effect has been proposed.

Highly sensitive and stable SERS probes of alternately deposited Ag and Au layers on 3D SiO2 nanogrids for detection of trace mercury ions

The hazard of Hg ion pollution triggers the motivation to explore a fast, sensitive, and reliable detection method. Here, we design and fabricate novel 36-nm-thick Ag-Au composite layers alternately deposited on three-dimensional （3D） periodic SiO2 nanogrids as surface-enhanced Raman scattering （SERS） probes. The SERS effects of the probes depend mainly on the positions and intensities of their localized surface plasmon resonance （LSPR） peaks, which is confirmed by the absorption spectra from finite-difference time-domain （FDTD） calculations. By optimizing the structure and material to maximize the intrinsic electric field enhancement based on the design method of 3D periodic SERS probes proposed, high performance of the Ag-Au/SiO2 nanogrid probes is achieved with the stability further enhanced by annealing. The optimized probes show the outstanding stability with only 4.0% SERS intensity change during 10-day storage, the excellent detection uniformity of 5.78% （RSD）, the detection limit of 5.0 × 10-12 M （1 ppt）, and superior selectivity for Hg ions. The present study renders it possible to realize the rapid and reliable detection of trace heavy metal ions by developing high- performance 3D periodic structure SERS probes by designing novel 3D structure and optimizing plasmonic material.

Propagation of shock waves in dry and wet sandstone:Experimental observations,theoretical analysis and meso-scale modeling

Methods of experimental observations, theoretical analysis and meso-scale modeling were used to study the propagation processes of shock waves in dry and wet sandstone under dynamic impact in this paper.According to the results from the dynamic impact experiments with velocity of 0.2-0.5 km/s, it was found that the velocity of shock wave increases linearly with water content. Additionally, the velocity of the shock wave in the sandstone showed a linearly increased regularity with the increasement of the impact velocity, which was proved by theory in this paper. Furthermore, meso-scale simulation models were performed and the simulation results showed that sandstone's porosity reduced the shock waves velocity compared to nonporous materials. Pore space filled with water counteracts the effects of porosity, resulted in larger shock wave velocity.

Damage characteristics of YAG transparent ceramics under different loading conditions

YAG (Y_(3)Al_(5)O_(12)) transparent ceramics have attractive application prospects for transparent armor protection modules because of their excellent light transmittance and anti-ballistic capability. Understanding the fracture behavior and damage mechanism of YAG is necessary for armor design. To explore the damage characteristics of YAG under compression and tension, shock compression and shockless spalling experiments with soft recovery technique are conducted. The spall strength of YAG is obtained and the recovered samples are observed by CT and SEM. It is shown that the macroscopic damage characteristic of YAG under compression is vertical split cracks with oblique fine cracks distributed in the entire sample, while that under tension is horizontal transgranular cracks concentrated near the main spall surface. The cracks generated by macroscopic compression, tension and shear stress extend in similar tensile form at the microscale. The proportion of transgranular fractures on spall surfaces is higher than that of cracks induced by macroscopic compression. Meanwhile, higher loading rate and longer loading duration increase the transgranular fracture percentage.

Systemic lupus erythematosus presenting with progressive massive ascites and CA-125 elevation indicating Tjalma syndrome?A case report

BACKGROUND Ascites,pleural effusion and raised CA-125 in the absence of malignancy in systemic lupus erythematosus is known as Tjalma syndrome.CASE SUMMARY We report a special case of a systemic lupus erythematosus patient presenting with Tjalma syndrome.She presented with ascites and elevated CA-125 in the absence of benign or malignant ovarian tumor and no pleural effusions,which is an unusual presentation for this rare condition.CONCLUSION Tjalma syndrome can present with massive ascites alone without pleural or pericardial effusions.

Hyperprolactinemia due to pituitary metastasis: A case report

BACKGROUND Pituitary metastasis is an uncommon manifestation of systemic malignant tumors.Moreover,hyperprolactinemia and overall hypopituitarism caused by metastatic spread leading to the initial symptoms are rare.CASE SUMMARY A 53-year-old male patient was admitted to our hospital with complaints of bilateral blurred vision,dizziness,polyuria,nocturia,severe fatigue and somnolence,decreased libido,and intermittent nausea and vomiting for more than 6 mo.During the last 7 d,the dizziness had worsened.Laboratory investigations revealed overall hypofunction of the pituitary gland,but the patient had an elevated serum prolactin level(703.35 mg/mL).Preoperative magnetic resonance imaging revealed a tumor in the sellar region,accompanied by intratumoral hemorrhage and calcification.Thus,transnasal subtotal resection of the lesion in the sellar region was performed.The histopathological and immunohistochemical examinations of the resected lesion revealed metastasis of lung adenocarcinoma to the pituitary gland.Oral hydrocortisone(30 mg/d)and levothyroxine(25 mg/d)were given both pre-and postoperatively.Postoperatively,the clinical symptoms were significantly improved.However,4 mo following the surgery,the patient succumbed due to multiple organ failure.CONCLUSION Hyperprolactinemia is one of the markers of poor prognosis in patients with carcinoma that metastasizes to the pituitary gland.Exogenous hormone supplementation plays a positive role in relieving the symptoms of patients and improving quality of life.

Oral berberine improves brain dopa/dopamine levels to ameliorate Parkinson’s disease by regulating gut microbiota

The phenylalanine-tyrosine-dopa-dopamine pathway provides dopamine to the brain.Iin this process,tyrosine hydroxylase(TH)isthe rate-limiting enzyme that hydroxylates tyrosine and generates levodopa(L-dopa)with tetranydrobiopterin(BH_(4))as a coenzyme.Here,we show that oral berberine(BBR)might supply H^(·) through dihydroberberine(reduced BBR produced by bacterial nitroreductase)and promote the production of BHl from dihydrobiopterin;the increased BH,enhances TH activity,which accelerates the production of L-dopa by the gut bacteria.Oral BBR acts in a way similar to vitamins.The L-dopa produced by theintestinal bacteria enters the brain through the circulation and is transformed to dopamine.To verify the gut-brain dialog activatedby BBR's effect,Enterococcus foecalis or Enterococcus faecium was transplanted into Parkinson's disease(PD)mice.The bacteriasignificantly increased brain dopamine and ameliorated PD manifestation in mice;additionally,combination of BBR with bacteriashowed better therapeutic effect than that with bacteria alone.Moreover,2,4,6-trimethy-pyranylium tetrafluoroborate(TMP-TFB)-derivatized matrix-assisted laser desorption mass spectrometry(MALDI-MS)imaging of dopamine identihed elevated striataldopamine levels in mouse brains with oral Enterococcus,and BBR strengthened the imaging intensity of brain dopamine.Theseresults demonstrated that BBR was an agonist of TH in Enterococcus and could lead to the production of L-dopa in the gut.Furthermore,a study of 28 patients with hyperlipidemia conhrmed that oral BBR increased bloodfecal L-dopa by the intestinalbacteria.Hence,BBR might improve the brain function by upregulating the biosynthesis of-dopa in the gut microbiota through avitamin-like effect.

Berberine treats atherosclerosis via a vitamine-like effect downregulating Choline-TMA-TMAO production pathway in gut microbiota

Trimethylamine-N-oxide(TMAO)derived from the gut microbiota is an atherogenic metabolite.This study investigates whether or not berberine(BBR)could reduce TMAO production in the gut microbiota and treat atherosclerosis.Effects of BBR on TMAO production in the gut microbiota,as well as on plaque development in atherosclerosis were investigated in the culture of animal intestinal bacterial,HFD-fed animals and atherosclerotic patients,respectively.We found that oral BBR in animals lowers TMAO biosynthesis in intestine through interacting with the enzyme/co-enzyme of choline-trimethylamine lyase(CutC)and flavincontaining monooxygenase(FMO)in the gut microbiota.This action was performed by BBR’s metabolite dihydroberberine(a reductive BBR by nitroreductase in the gut microbiota),via a vitamine-like effect down-regulating Choline-TMA-TMAO production pathway.Oral BBR decreased TMAO production in animal intestine,lowered blood TMAO and interrupted plaque formation in blood vessels in the HFD-fed hamsters.Moreover,21 patients with atherosclerosis exhibited the average decrease of plaque score by 3.2%after oral BBR(0.5 g,bid)for 4 months(^(*)P<0.05,n=21);whereas the plaque score in patients treated with rosuvastatin plus aspirin,or clopidogrel sulfate or ticagrelor(4 months,n=12)increased by 1.9%.TMA and TMAO in patients decreased by 38 and 29%in faeces(^(*)P<0.05;^(*)P<0.05),and 37 and 35%in plasma(^(***)P<0.001;^(*)P<0.05),after 4 months on BBR.BBR might treat atherosclerotic plaque at least partially through decreasing TMAO in a mode of action similar to that of vitamins.

Enantiomeric separations of four basic drugs containing N-alkyl groups by a RP-HPLC system using SBE-β-CD as chiral mobile phase additive

The chiral separations of four pharmaceutical racemates which contain N-alkyl groups were satisfactorily resolved using SBE-β-CD as a chiral mobile phase additive （CMPA） in a RP-HPLC system （the resolution is 2.701 for ondansetron hydrochloride, 1.996 for sulpiride, 1.293 for clenbuterol hydrochloride and 0.816 for omeprazole）. In addition, the effects of different parameters such as CD type and CD concentration were investigated. The separation mechanism arises through the combination of several potential interactions, including electrostatic interactions as well as hydrogen bonding interactions and hydrophobic inclusion interactions, which allow for the SBE-β-CD-drug complexation with strong stereoselectivity and stability. The resolution also relates to the number and location of N atoms in the enantiomers. This method will be applicable to the isolation of various types of biologically imoortant enantiomers containing N-alkyl groups.