As the present research results on all

As the present research results on all kinds of semiconductor metal oxides have shown, ZnO may be one of the most hopeful candidates due to its mature fabrication technology, which can produce all kinds of ZnO nanostructures, such as nanowires, nanorods, nanobelts [12], nanoribbons, etc.
It is well known that the sensing performance of the gas sensors can be enhanced by adjustment of the microstructure, doping of dopant or using a small amount of noble catalyst, etc. [13–17]. Although it LY2606368 Supplier is proved that the nanocrystalline ZnO is one of the most promising metal oxides for gas sensors due to the unique conductance characteristics and large surface to volume ratio, their sensing performances can also be improved dramatically by the synergistic effects of the catalyst or dopant on the pure nanocrystalline ZnO.
Even though many ZnO-based gas sensing elements with high specific surface areas have been investigated and reported [18], and some of their grain sizes are as low as a few tens of nanometers, their gas sensitivities deriving from these ZnO nanomaterials have not been greatly enhanced as yet. The reasons for this phenomenon have not been discussed systematically up to now.
The sol–gel process is defined generally as: the process that involves the transition of a system from a liquid “sol” (mostly colloidal) into a solid “gel” phase [19]. Hydrolysis, condensation and drying are tree key steps in determining the properties of the final product in sol–gel processing. Sol–gel processes have several advantages over other techniques for synthesizing nanopowders of metal oxides. These include the production of ultrafine porous powders and homogeneity of the product as a result of homogenous mixing of the starting materials on the molecular level. Also, sol–gel processing holds strong promise for employment industrially on large scales [20]. In this work we have chosen the sol–gel technique for the previous advantages.

Materials and methods

Results and discussion

The main objective of presence work was attaining ZnO gas sensor devices with high sensitivity for gas detection via double and quadrature gas sensor array. Undoped and Al-doped ZnO nanopowders with were synthesized using the sol–gel method. Structural investigations, performed by X-ray diffraction technique indicate that, studied samples are polycrystalline hexagonal wurtzite structure. Surface morphology for Undoped and Al-doped ZnO nanopowders were analyzed by scanning electron microscopy. Chemical composition of Al-doped ZnO nanopowders was performed using energy dispersive X-ray (EDS) analysis for different doping ratios. Three kinds of gases were analyzed via both double and quadrature gas sensor devices using homemade gas chamber. For oxygen gas, the best doping ratio that has a maximum oxygen sensitivity was recorded at Zn:Al=99:1, which provided maximum sensitivity 90%. The fabricated gas sensor devices attain low carbon dioxide gas response, where the maximum CO2 sensitivity recorded for the Al doped ZnO gas sensors with dopant ratio for ZnO:Al of 95:5 that equal 94%. The highest sensitivity values for both double and quadrature gas sensor devices established for H2 gas. The maximum sensitivity is given at Zn:Al=95:5 weight ratio, that get to 98%.

Conflict of interest

br Materials and methods br Results Microfluidic analytical

Materials and methods

Microfluidic analytical devices with optical detection are considered one of the best options for developing robust and sensitive lab-on-chip devices. Key features for diagnostic and prognostic usefulness of such devices are high sensitivity and specificity, ability to provide quantitative information and multiplexing capability. On the other hand, one of the main challenges for real life applications and commercial exploitation is full integration, which includes the open issue of coupling the lab-on-chip with a portable and miniaturized detector [1].
The use of CL detection in a disposable microfluidic chip with integrated array of a:Si-H photosensors has been previously shown to provide excellent analytical performance in enzyme assays and immunoassays applications, along with detector on-chip integration, optimal optical coupling, device compactness and reduced power consumption and memory occupancy [14].

In the present work, the performance of a portable analytical device based on a disposable microfluidic cartridge integrated with an array of 30 a-Si:H photosensors for CL detection of viral DNA was evaluated. In particular a microfluidic reaction chip was designed comprising a PDMS microfluidic layer coupled with a glass slide on which genotype specific B19 capture oligonucleotide probes had been arrayed. The reaction chip was then integrated with the array of photosensors, aligning each photosensor with one oligonucleotide probe spot in order to monitor luminescent signals. Both the reaction chip and the a-Si:H photosensors are inexpensive to manufacture and suitable for the development of portable analytical devices. The design of the reaction chip combined with the array of photosensors make it possible to detect simultaneously three B19 DNA in a unique analysis. Moreover the specificity of the oligoprobes and the sensitivity of photosensors allowed an accurate quantification of the target analyte. In fact, target detectability was 0.07nmolL for the three different B19 DNA genotypes which is comparable to the LOD of 0.1nmolL obtained both for the Phos-tag step of B19 amplified products in conventional assay formats (e.g., PCR-ELISA methods) or exploiting other portable detection systems (e.g., CCD camera) [25]. Moreover the photosensors showed low instrumental noise levels, good reproducibility and negligible crosstalk between adjacent sensors.

Financial support was provided by the Italian Ministry of Instruction, University and Research (MIUR): PRIN 2010-2011 project: prot. 20108ZSRTR “ARTEMIDE (Autonomous Real Time Embedded Multi-analyte Integrated Detection Environment): a fully integrated lab-on-chip for early diagnosis of viral infections”.

Biosensors for the direct detection of biomolecules at the single molecule level would be highly desirable for a range of diagnostic applications, especially if these bioanalytes could be delivered sequentially through a nanopore. So far, metallic nanostructures have been shown to provide an enhancement factor of 1014 with a large cross-sectional area of 10cm2/molecule using surface enhanced Raman scattering approaches [1]. The rational design of metallic nanostructures for this application, also known as plasmonic substrates or devices, for sensing applications is well established [2]; the functional characteristics of these devices are based upon the behaviour of plasmons at the interface of a metal-dielectric medium. For metallic nanostructures, the electrons in the metal are excited and oscillate within the metal core near the interface with a surrounding dielectric material; these collective electron excitations are known as surface plasmon polaritons.
The potential of nanostructured metallic structures for optical applications has been demonstrated for (i) biosensing applications [3], (ii) surface enhanced Raman spectroscopy (SERS) [4], (iii) guiding and manipulating the light [5], (iv) sub-diffraction limited imaging [6] and (v) trapping of micro/nano-sized particles [7]. In order to apply the nanostructures for these applications, the structure dimensions and geometry have to be appropriate for (i) tuning of the plasmon resonance coupling, (ii) the near field enhancement, (iii) the confinement in sub-wavelength region coupling, (iv) enhanced evanescent waves and (v) the near- and far-field enhancement, [8] respectively to each application. Moreover it is essential that there are high levels of local-electric field intensity at locations within the sensor where the plasmon enhancement of signal from the transducer will be most beneficial — this is especially true for sensing applications where the analyte must be within the region of highest electric field (E-field) intensity. Various metallic nanostructures have been proposed for sensing using a range of different shapes and geometries [9], materials [10,11] and fabrication methods [12], notably for the optimization of SERS measurements [13] tip-enhanced Raman scattering, (TERS) [14] and fluorescent enhancement [15]. Most of the nanostructures studied so far are multi-scale nanoparticles and nanocrystals. The nanoparticles can be classified as 1-dimensional [16], 2-dimensional and 3-dimensional nanoparticles i.e., nanorods, nanocrescent and nanopores respectively. More recently planar plasmonic substrates have been developed for ‘nanofocusing of plasmons’ [17–22] and SERS [23,24].

Bambuterol is a prodrug of the

Bambuterol is a prodrug of the β2-agonist terbutaline. It is commonly prescribed for catalase inhibitor and chronic obstructive pulmonary disease (COPD) with once daily dosing and documented clinical safety (Olsson and Svensson, 1984; D\’Alonzo et al., 1995; Sitar et al., 1993). It has been reported previously that bambuterol increases the level of high-density lipoprotein cholesterol (HDL-C) in patients with hyperlipidemia (FlorÉN et al., 1997) and in patients with type II diabetes mellitus (Bitzén et al., 1993) after six to eight weeks of treatments. However, the cholesterol lowering effect of bambuterol, particularly on the level of LDL-C, was only marginal and inconclusive (FlorÉN et al., 1997; Bitzén et al., 1993). Bambuterol is a chiral drug with R- and S-enantiomers (Gazić et al., 2006). The uncertain LDL-C lowering effect of bambuterol in the previous studies might be related to the inefficacy of racemic bambuterol due to the different biological effects of enantiomers (Waldeck, 1993). Animal study clearly suggested a cholesterol lowering effect of R-bambuterol in the treatment of tyloxapol-induced hyperlipidemia in mice (Cheng and Tan, 2009). In addition, the previously inconclusive effects on plasma lipid of bambuterol were shown in long term studies without a demonstration of a dose relationship.



High plasma level of LDL-C is a major risk factor for coronary heart disease. Conventional cholesterol-lowering treatments such as statin are only modestly effective. Bambuterol is a type of β2-agonist commonly used for the treatment of asthma and COPD with the advantage of once daily dosing and favorable side effect profile (Olsson and Svensson, 1984; D\’Alonzo et al., 1995; Sitar et al., 1993). In this open-label, randomized phase I clinical trial, we showed that R-bambuterol significantly lower the plasma levels of LDL-C, and marginally raise the ratio of ApoA1/ApoB, an indicator of HDL-C/LDL-C, in less than 2h after administration and in a dose-dependent manner. We also showed that R-bambuterol is more potent in cholesterol lowering than rac-bambuterol. The lipid-lowing effects of R-bambuterol sustained after 24h of treatment and after multiple doses. R-bambuterol therefore is an attractive alternative or complement for other treatments to decrease plasma LDL-C levels, and would be especially beneficial for those patients who also suffering from COPD.
The lipid-lowering effect of R-bambuterol was dose-dependent (Fig. 2). A single dose of R-BMB significantly lowered the levels of LDL-C and marginally raised the ratio of ApoA1/ApoB at Tmax (less than 2h), therefore achieved a favorable lipid lowering effect in a short term. Correlation between Cmax of R-bambuterol and the corresponding lipid levels at Tmax further supported the lipid-lowering effect of R-bambuterol (Suppl. Fig. 1).
The lipid-lowering effect of R-bambuterol was also observed at 24h catalase inhibitor after dosing, which appeared to be weaker. At 24h, the concentration of plasma R-bambuterol was less than one tenth of that at Tmax (Table 2). It indicated that multiple mechanisms underlie the lipid-lowering effects of R-bambuterol, namely the initial effects and the lagging effects. The initial effects were possibly related to the inhibition of butyrylcholinesterase (Gazić et al., 2006). Butyrylcholinesterase activity has been associated with cardiovascular risk factors, including the level of LDL-C (Stojanov et al., 2011). The lagging effects were unlikely to be related to terbutaline since the concentration of terbutaline at 24h after treatment (Table 2) was much lower compared to the previous study (Hooper et al., 1981). In the multiple-dose 5mg R-bambuterol group, the reduction in LDL-C and the increase in ApoA1/ApoB at 24h after dose 6 and dose 7 were comparable to those in the single-dose group. These results suggested potential long-term cholesterol-lowering effects of R-bambuterol.
The lipid-lowering effects of R-bambuterol and rac-bambuterol were compared. At Tmax, percentage changes in LDL-C, TC, ApoB and ApoA1 in the 10mg rac-bambuterol group were similar to those in the 5mg R-bambuterol group, but only approximately half of those in the 10mg R-bambuterol group (Fig. 3), suggesting that R-bambuterol was more potent. R-bambuterol made up half of rac-bambuterol. It is possible that R-enantiomer of bambuterol is the eutomer which accounted for most of the observed cholesterol-lowering effects of rac-bambuterol. Similar findings in previous study in guinea pigs showed that the protective effect of R-bambuterol from histamine induced bronchoconstriction is stronger than that of rac-bambuterol (Cheng and Tan, 2009).

Previous research has described the effects of eight week mindfulness

Previous research has described the effects of eight-week mindfulness meditation instruction on neural connectivity (e.g., ), and Shao further extends this work. The Shao study is a note-worthy contribution, especially related to the rigorous randomized active-control study design, longitudinal approach, and correlation of affective and neural connectivity changes. Shao et al. have chosen a relaxation program control condition in order to discern the effects of meditation instruction beyond non-specific benefits of a positive peer-group activity. The longitudinal nature of the trial further strengthens the findings, as differences in changes between study arms seen post-group are attributable to the meditation aspect of the intervention. Given these methodological strengths, the authors show salient effects of the eight-week meditation program related to resting state neural connectivity (increased connectivity from the pons to posterior cingulate melanocortin receptor (PCC)/precuneus) and affective processing (“neutralizing” affective processing of positive and negative stimuli). Further, the resting state changes in neural connectivity from pons to PCC/precuneus predicted the changes in affective processing, suggesting that the eight-week meditation program leads to changes in the regulatory neural network both during affective evaluation and at rest. These are notable findings further illustrating the complex interplay between neural connectivity and affective processing. Additional research is needed to examine the clinical implications of this work among elderly patients and to explore the generalizability of the findings to other populations.

Recently, published a study proposing that clevidipine\’s complex mechanism of action might be responsible for relieving dyspnea in acute heart failure (AHF) patients . Clevidipine was approved by Food and Drug Administration (FDA) (2008) as a third generation dihydropyridine (DHP) calcium channel blocker for the management of perioperative acute hypertension (; ). In 2014, Peacock et al. published the results of a randomized, open-label active control study (PRONTO) evaluating the efficacy of clevidipine versus standard of care (SOC) anti-hypertensive therapy and concluded that clevidipine was responsible for a rapid reduction in blood pressure and dyspnea improvement in hypertensive AHF patients ().
Calcium influx during depolarization in vascular smooth muscle (VSM) is prevented by clevidipine administration, blocking intracellular phosphodiesterase with an increase in guanosine monophosphate. This mechanism is responsible for an inhibition in VSM contractility associated with cardiopulmonary and systemic vasodilation (). A reverse translational medicine approach was used by in order to test the idea that, in human lungs, a unique combination of Ca1.2 splice variants is expressed with a higher affinity for clevidipine than the same splice variant in other tissue. The authors refine the general understanding of how pannexin-1 (Panx1), known to act as a major adenosine triphosphate (ATP) release channel, affects Ca1.2 pharmacology and increases its affinity for clevidipine. Further research was encouraged in order to clarify the role of splice variants to the pathophysiology of AHF in the light of a new paradigm generated by Panx1/Ca1.2 interaction ().
acknowledged the extended body of research conducted over the last 18years since clevidipine was approved as an investigational new drug, and its importance in gaining a better understanding of its mechanism of action (). Their work focused on testing the hypothesis that specific CACNA1C splice variants are encoding for Ca1.2 in lung tissue with a different pharmacological profile for clevidipine when compared to the same variants expressed in other tissues. They also considered the hypothesis that clevidipine-induced dyspnea relief is due to clevidipine acting on Panx1 channels in lung tissue. The authors considered the possibility that Panx1 associates with Ca1.2 in lung tissue, resulting in an increased affinity of Ca1.2 for clevidipine ().

Autophagy also plays a role

Autophagy also plays a role in response to treatment. An extensive literature suggests that autophagy can protect cancer cells against commonly used cancer therapies including a wide array of different drugs and radiation (Thorburn et al., 2014; Rebecca and Amaravadi, 2015). Such studies are the basis for most of the current efforts to target autophagy in patients (Table 2). Perhaps even more important than chemo-sensitization, autophagy inhibition may overcome acquired resistance to other anti-cancer agents. The best evidence for this is in tumors with activating mutations in BRAF that have become resistant to BRAF inhibitors like vemurafenib. Vemurafenib resistance in melanoma is associated with increased autophagy and autophagy inhibition can reverse resistance associated with endoplasmic reticulum stress (Ma et al., 2014). There is also evidence that autophagy inhibition to overcome drug resistance can be effective in patients. A MG-132 cancer patient with a BRAF mutant tumor that had become resistant to vemurafenib was successfully treated with a combination of CQ and vemurafenib experiencing long term tumor regression on the combination treatment (Levy et al., 2014). Importantly, this patient had periods of time when the autophagy inhibitor CQ was maintained but the BRAF inhibitor was discontinued for periods of time. In every instance, this led to increased tumor growth that was reversed when the combination treatment was re-established. This case study is the first to suggest that autophagy inhibition with CQ can overcome acquired resistance to the kinase inhibitor but that only combination treatment with both the BRAF inhibitor and the autophagy inhibitor is effective. Continued follow up of this patient has demonstrated sustained tumor regression for over two and a half years and more recent studies submitted for publication from Mulcahy-Levy et al. have extended these findings to two other patients both of whom acquired resistance to vemurafenib following successful therapy and then experienced clinical improvement on the combination of CQ and vemurafenib.
Although most current clinical trials (Table 2) involve autophagy inhibition, there are arguments against this idea often revolving around effects of autophagy inhibition on the immune response to cancer (Zhong et al., 2016). It has been reported that “immunogenic” tumor cell killing– i.e. killing cancer cells with chemotherapy in a way that will lead to effective engagement of an anti-tumor immune response – requires that the dying cancer cells have functional autophagy (Michaud et al., 2011) leading to suggestions that we should try to enhance autophagy to improve cancer immunotherapy (Zhong et al., 2016). Consistent with this idea, a recent study concluded that caloric restriction could enhance tumor immunosurveillance only for autophagy-proficient tumors (Pietrocola et al., 2016). However, autophagy inhibition can enhance immune cell-mediated, anti-tumor effects under at least some circumstances (Liang et al., 2012; Baginska et al., 2013). More work is needed to better understand the interplay between autophagy\’s role(s) in the anti-tumor immune response.

Clinical Trials of Targeted Autophagy Inhibition
Despite the caveats discussed above, there are already many studies attempting to inhibit autophagy in cancer therapy. All the current studies use CQ or HCQ. These drugs inhibit the lysosome and block autophagy while causing accumulation of autophagosomes and LC3, which have been used as pharmacodynamic markers of the inhibitor\’s activity. CQ and HCQ are inexpensive, approved drugs that have been used for decades to treat malaria and arthritis but have some caveats as autophagy inhibitors. First, they can have anti-tumor effects through other mechanisms such as reducing nutrient scavenging and can sensitize to other chemotherapies by autophagy-independent mechanisms (Eng et al., 2016; Maycotte et al., 2012). Second, alterations in tumor pH may affect drug bioavailability (Pellegrini et al., 2014).

FH535 br Discussion Cryptococcosis is an

Cryptococcosis is an opportunistic infection caused by encapsulated yeast, C neoformans. This pathogen is found in soil, fruit, vegetables, decaying wood, and the FH535 of many birds, especially pigeons. It usually emerges in immunocompromised patients, such as those with a history of underlying malignancy, organ transplant, acquired immunodeficiency syndrome, or corticosteroid therapy, although occasionally it may occur in immunocompetent hosts.
Cutaneous cryptococcosis usually results from hematogenous dissemination from other distant organs in immunocompromised hosts, referred to as secondary cutaneous cryptococcosis (SCC). The airway is believed be the main entry portal. Cutaneous involvement occurs in FH535 10-20% of cases of disseminated cryptococcosis. However, direct inoculation is a possible route, which causes primary cutaneous cryptococcosis (PCC). A history of trauma is the most frequently reported risk factor to provide a portal of entry, and foreign body puncture and animal-related trauma are the most common related causes. Patients with hobbies or occupations that put them at risk of injuries with exposure to soil, dust, wood sticks or debris, or bird droppings are at the greatest risk of PCC. The mean duration between inoculation and clinical manifestation is usually 8 days. In addition, C neoformans var. neoformans has a lower thermotolerance compared with the other serotypes, which may explain its dermatotrophism.
The diverse clinical manifestations of PCC include papules, pustules, nodules, plaques, vesicles, ulcers, ecchymosis, cellulitis, subcutaneous lesions resembling erythema nodosum, herpetiform or molluscum contagiosum-like lesions, and polymorphic lesions. Therefore, cutaneous cryptococcosis should be suspected if the skin eruptions respond poorly to standard treatment, and a diagnostic skin biopsy should be performed.
The rare cases of PCC usually have favorable outcomes, even in immunocompromised patients. Compared with patients with SCC, patients with PCC tend to be older and are characterized by a lack of underlying systemic disease. Additionally, patients with PCC tend to reside in rural areas whereas those with SCC tend to reside in urban areas. The two diseases have a similar male-to-female ratio (approximately 1:1). Indicators of PCC include an absence of dissemination, solitary skin lesions on unclothed areas, history of skin injury, participation in outdoor activities or exposure to bird droppings, and isolation of C neoformans serotype D. However, Xiujiao and Ai\’e observed that the presence of C neoformans serotype D may not be an essential criterion for a diagnosis of PCC because both C gattii and C neoformans var. neoformans can also lead to infection in immunocompetent hosts. In immunocompetent hosts, the most common sites of lesions are the facial area and upper extremities. Immunocompromised hosts are characterized by multiple lesions, typically in the trunk or lower extremities.
A diagnosis of PCC should be considered a diagnosis of exclusion, because cutaneous lesions are a symptom of systemic cryptococcosis. Extensive work-ups including a detailed history, physical examination, and laboratory examination are essential to exclude dissemination. A lumbar puncture is indicated when symptoms of central nervous system (CNS) involvement are present; however, its usefulness is debatable in the absence of localizing signs. Underlying immunodeficiency should also be evaluated.
Because the optimal treatment regimen for cutaneous cryptococcosis is not well established, treatment usually varies according to the extent of disease and host immunocompetence. In immunocompetent patients, the Infectious Disease Society of America guidelines recommend treating cryptococcal CNS infection or dissemination with amphotericin B (0.7-1 mg/kg/day) plus flucytosine (100 mg/kg/day) for at least 4 weeks, followed by consolidation therapy with fluconazole (400-800 mg/day) for a minimum of 8 weeks and maintenance therapy with fluconazole (200 mg/day) for 6-12 months. As for pulmonary disease, fluconazole 400 mg daily for 6-12 months is recommended in mild to moderate disease. The regimen differs in severe or progressive disease, which is the same as treating CNS involvement. Secondary cutaneous cryptococcosis is treated in a manner similar to that of CNS infection, whereas fluconazole 400 mg daily for 6-12 months is recommended to treat PCC in an immunocompetent host. However, a short-term (2 weeks) course of fluconazole treatment (200 mg daily) has also proven to be effective in PCC.

Introduction ZrB is the leading

ZrB2 is the leading material among ultra-high-temperature ceramics due to its high melting point (3245 °C), high hardness (23 GPa), high thermal conductivity (∼60 W m−1 ·k−1), electrical conductivity (∼107 S m−1), and relatively low density (6.09 g cm−3), high strength at elevated temperatures, and stability in extreme environments [1]. The addition of SiC and carbon can inhibit the grain growth, improve the sinterability, and increase the thermal and mechanical properties and oxidation resistance [2,3]. ZrB2–SiC based ceramics are attractive for aerospace applications such as thermal protection systems, leading edges, trailing edges, and propulsion components for hypersonic flight vehicles [4,5].
The components of ZrB2–SiC composite are generally made by pressureless sintering (PS) or hot pressing (HP). The difficulty in fabricating the large size or complex shapes limits the application of ZrB2–SiC composites. Joining is an alternative and cost effective method for fabricating the large size or complicated shape components of ceramics. Joining of engineering ceramics such as Al2O3, SiC, C/C, C/SiC has been widely studied [6–11]. Recently, several investigations on joining of ZrB2–SiC composites have been reported in the literature. Bellosi et al. [12] joined ZrB2–SiC composites using Ca–Al–Si–O, and Y–Al–Si–O glass powders as bonding inter layers at 1440 °C and reported a bending strength of 277 MPa at room temperature. Among other reports, brazing is the most common method. Muolo et al. [13] studied the wetting behavior of ZrB2 with different metals (Cu, Ag, Au) and their alloys and optimal results were obtained with silver-based alloys. Due to low melting point of these solders, the joints cannot be useful at temperature above 1000 °C.
Singh et al. [14] studied the joining of ZrB2–SiC9–SiC, ZrB2–SiC–C and ZrB2–SiC to themselves and to commercially pure Ti using boron containing Ni Gefitinib braze alloys (MBF-20 and MBF-30). Asthana et al. [15] studied the joining of similar composites to themselves using Pd-based brazes Palco (65% Pd-35% Co) and Palni (60% Pd-40% Ni). Hair line cracks, substantial chemical interaction and interfacial cracking due to residual stresses were observed.
Practical applications also require joining of ZrB2–SiC composites to refractory metals like Nb and its alloys. Bo et al. [16] joined the monolithic ZrB2 and ZrB2–SiC composites to themselves using pure Ni powder. The maximum shear strengths of 59.7 ± 5.3 MPa and 43.4 ± 7.5 MPa were obtained for ZrB2 and ZrB2–SiC joints, respectively. Peng et al. [17] diffusionally bonded ZrB2–SiC composites to Nb using Ti interlayer to synthesize TiB whiskers array insitu and reported a maximum shear strength of 158 MPa. Yang et al. [18] diffusionally bonded ZrB2–SiC to Nb using dynamically compressed Ni foam interlayer and reported a maximum shear strength of 155.6 MPa.
Though arc welding of ZrB2 is possible due to its electrical conductivity [19], the research on joining by gas tungsten arc welding (GTAW) or plasma arc welding is very limited. Brown et al. [20] reported fusion welding of ZrB2-20 vol% SiC and ZrB2–SiC–B4C composites. By preheating and controlled cooling under protective atmosphere the 3 mm-thick parts were joined by GTAW. The strength of joints was ¼ of the strength of parent material. Thermal conductivity of joints was higher than that of parent material. Very recently King et al. [21] reported the plasma arc welding of TiB2 – 20 vol % TiC composites and ZrB2-20 vol % ZrC composites [22] achieved by preheating the weld coupons to 150 °C.
In the present work, a filler material of (ZrB2–SiC–B4C–YAG) composite with oxidation resistance and thermal shock resistance has been produced in the form of welding rods. The filler was used in GTAW of HP (ZrB2 – 20 vol.% SiC), and PS (ZrB2 – 20 vol.% SiC – 8 vol.% B4C – 7 vol.% YAG) composites. Without any preheating, post controlled cooling, and extraneous protective gas shield, GTAW was performed manually.

br Theoretical model and numerical method br Results and discussion

Theoretical model and numerical method

Results and discussion
A 3D transient analysis of a solid-armature railgun was examined. The mesh of coupled multi-field model including armature and rails is shown in Fig. 1. The unit of geometric size in Fig. 1 is millimeter. The initial conductor temperature was set to 25 °C.
Table 1 lists the material properties used in calculation. The symbols σ, ρ, E, ν, c and κ represent electrical conductivity, density, modulus of elasticity, Poisson\’s ratio, heat capacity and thermal conductivity, respectively.
Pulsed current was applied on the breech segment of railgun model. The armature was accelerated by the Lorentz force, which is generated by the action of current and magnetic fields. The profiles of the imposed current and armature velocity are shown in Fig. 2. The armature velocity reached 2623 m/s.


In-bore yaw of a projectile in a gun tube has been shown to result in range loss if the yaw is significant [1]. Kent [2,3] and later, Sterne [4], developed the following equations that related in-bore yaw to First Maximum Yaw (FMY).
In this equation, IT and IP are the projectile\’s transverse and polar moments of inertia, respectively, Sg is the gyroscopic stability factor, and δtm is the (small) angle of the projectile in the bore of the weapon at the instant of muzzle exit. We can write this in terms of bore clearance. If we assume that the wheel Calcium Ionophore I of the projectile is determined by the longest distance between the largest diameters of the forward and aft bourrelets (lbb) and assuming small angles, we can writewhere dbore is the diameter of the bore, d is the projectile bourrelet diameter and δtm is the in-bore yaw in radians. These equations were later implemented and plotted against test results in the experimental firings of Kent and Hitchcock [5].
In 2012, experiments were conducted at Yuma Proving Ground during an effort to determine the effect that severely worn lands at the muzzle of a 155 mm howitzer would have on the range of a projectile [6].
The FMY described in Eq. (1) is physically generated by the spinning of a yawed projectile, irrespective of the gas dynamics about that projectile. If the weapon has a muzzle brake or other muzzle device, the gas dynamics will likely have more of an effect on the yaw because the projectile is not constrained by the bore during the initial stages of gas ejection.
Measuring the pressure distribution in the muzzle brake is problematic due to the weapon geometry. Pressure gages can easily be placed on the baffle surfaces but determination of the pressure in the flow channels is problematic. Placement of a gage in the flow channels of a muzzle brake has to meet two diametrically opposed criteria: The gage has to remain stationary while hot, high pressure gases blow by it and yet has to be so non-invasive as to not affect the flow. Non-invasive mounting techniques will not survive the gas flow and mounts that are sturdy enough to survive invariably affect the gas flow. Because of this, it was decided to mount twelve pressure transducers, in three sets of four, at a position somewhat up-bore of the muzzle brake. A picture of the mounted gages is shown in Fig. 1.

Test description

Pressure data collection
Blow-by pressure was recorded at 10, 15, and 20 inches from the muzzle of the gun tube forming cross sectional planes B, C, and D respectively, each plane containing four pressure transducers 90° apart. The convention used for plane/sensor designation and for the blow-by analysis is as shown below, as viewed toward the muzzle and rotating clockwise starting at 12 o\’clock as 0° as shown in Fig. 2. This sensor orientation was configured to determine the blow-by pressure distribution along the side of the projectile in terms of time and was used to calculate the net overturning moment acting on the projectile.