Influence of Silicon Carbide on Direct Powder Bed Selective Laser Process (Sintering/Melting) of Alumina

The powder bed selective laser process (sintering/melting) has revolutionised many industries, including aerospace and biomedicine. However, PBSLP of ceramic remains a formidable challenge. Here, we present a unique slurry-based approach for fabricating high-strength ceramic components instead of traditional PBSLP. A special PBSLP platform capable of 1000 °C pre-heating was designed for this purpose. In this paper, PBSLP of Al2O3 was accomplished at different SiC loads up to 20 wt%. Several specimens on different laser powers (120 W to 225 W) were printed. When the SiC content was 10 wt% or more, the chemical interaction made it difficult to process. Severe melt pool disturbances led to poor sintering and melting. The structural analysis revealed that the micro-structure was significantly affected by the weight fraction of SiC. Interestingly, when the content was less than 2 wt%, it showed significant improvement in the microstructure during PBSLP and no effects of LPS or chemical interaction. Particularly, a crack pinning effect could be clearly seen at 0.5 wt%.

Preparative-scale synthesis of nonacene

During the last years we have witnessed progressive evolution of preparation of acenes with length up to dodecacene by on-surface synthesis in ultra-high vacuum or generation of acenes up to decacene in solid matrices at low temperatures. While these protocols with very specific conditions produce the acenes in amount of few molecules, the strategies leading to the acenes in large quantities dawdle behind. Only recently and after 70 years of synthetic attempts, heptacene has been prepared in bulk phase. However, the preparative scale synthesis of higher homologues still remains a formidable challenge. Here we report the preparation and characterisation of nonacene and show its excellent thermal and in-time stability.

Highly Thermoconductive Yet Ultraflexible Polymer Composite with Superior Mechanical Properties and Autonomous Self-Healing Functionality via Binary Fillers Strategy

It is still a formidable challenge to develop ideal thermal dissipation materials with simultaneous high thermal conductivity, excellent mechanical softness and toughness, and spontaneous self-healing. Herein, we report the introduction...

Teacher Education in the Philippines: Are We Meeting the Demand for Quality?

The Philippines’ dismal performance in recent international assessments (e.g., PISA in 2018; TIMSS and SEA-PLM in 2019) evince that a learning crisis persists and remains a formidable challenge for the country. This is despite the many educational reforms undertaken in recent years, such as resolving the decades-long backlog in school infrastructure, expanding access to early childhood education, upgrading teacher salaries, and enhancing the basic education curriculum. Although there is a myriad of factors that contribute to poor learner outcomes, there is a consensus in literature regarding the central role played by the teacher in these dynamics. This has motivated the researchers’ study of teacher education programs in higher education institutions (HEIs), particularly in their capacity to effectively prepare pre-service teachers for the profession. To fully understand this phenomenon, the researchers explored the profile of teacher education programs in the country in the past decade, and used multiple regression analysis to examine the relationship between performance in the Licensure Exam for Teachers (LET) and the characteristics of the HEI attended (e.g., student-to-faculty ratio, HEI type, location, size, year established). It was found that between 2010 to 2016, an outsized proportion of poor quality were in Mindanao, particularly in BARMM and Region 12. Not coincidentally, these are the same regions where not a single institution has been able to hurdle CHED requirements to become a Center of Excellence (COE) in Teacher Education. Further analysis shows that attending programs in small HEIs is associated with a 14 to 17 percentage point disadvantage in the LET, relative to large institutions. Meanwhile, SUCs are seen to perform better in LET Elementary, whereas private HEIs and LUCs perform slightly better in LET Secondary. The proponents of this study put forward policy recommendations aimed at curbing the prevalence of non-performing HEIs, providing incentives for quality among TEIs, and strengthening oversight and coordination of the space.

Achieving High Performance Molecular Rectification through Fast Screening Alkanethiol Carboxylate-Metal Complexes Electro-Active Unites

Achieving high rectifying performance of molecular scale diode devices through synthetic chemistry and device construction remain a formidable challenge due to the complexity of the charge transport process and the device structure. We demonstrated here high-performance molecular rectification realized in self-assembled monolayer (SAM) based device by low-cost and fast screening the electroactive units. SAMs of commercial available carboxylate terminated alkane thiols on gold substrate, coordinated with a variety of metal ions, structures denoting as Au-S-(CH2)n-1COO-Mm+ (Cn+Mm+), where n=11, 12, 13, 14, 16, 18 and Mm+=Ca2+, Mn2+, Fe2+, Fe3+, Co2+, Ni2+, Cu2+, Zn2+, were prepared and junctions were measured using a eutectic indiumgallium alloy top contact (EGaIn). The C18+Ca2+ and C18+Zn2+ junctions were found to afford a record high rectification ratio (RR) of 756 at ±1.5 V. Theoretical analysis based on single level tunneling model shows that optimized combination of the asymmetry voltage division, energy barrier and the coupling of carboxylate-metal complex with electrode. Our method described here represent a general strategy for fast, cheap and effective exploration of the metal complex chemical space for high-performance molecular diodes devices.

Hydroxylation of N-acetylneuraminic Acid Influences the in vivo Tropism of N-linked Sialic Acid-Binding Adeno-Associated Viruses AAV1, AAV5, and AAV6

Adeno-associated virus (AAV) vectors are promising candidates for gene therapy. However, a number of recent preclinical large animal studies failed to translate into the clinic. This illustrates the formidable challenge of choosing the animal models that promise the best chance of a successful translation into the clinic. Several of the most common AAV serotypes use sialic acid (SIA) as their primary receptor. However, in contrast to most mammals, humans lack the enzyme CMAH, which hydroxylates cytidine monophosphate-N-acetylneuraminic acid (CMP-Neu5Ac) into cytidine monophosphate-N-glycolylneuraminic acid (CMP-Neu5Gc). As a result, human glycans only contain Neu5Ac and not Neu5Gc. Here, we investigate the tropism of AAV1, 5, 6 and 9 in wild-type C57BL/6J (WT) and CMAH knock-out (CMAH−/−) mice. All N-linked SIA-binding serotypes (AAV1, 5 and 6) showed significantly lower transduction of the heart in CMAH−/− when compared to WT mice (5–5.8-fold) and, strikingly, skeletal muscle transduction by AAV5 was almost 30-fold higher in CMAH−/− compared to WT mice. Importantly, the AAV tropism or distribution of expression among different organs was also affected. For AAV1, AAV5 and AAV6, expression in the heart compared to the liver was 4.6–8-fold higher in WT than in CMAH−/− mice, and for AAV5 the expression in the heart compared to the skeletal muscle was 57.3-fold higher in WT than in CMAH−/− mice. These data thus strongly suggest that the relative abundance of Neu5Ac and Neu5Gc plays a role in AAV tropism, and that results obtained in commonly used animal models might not translate into the clinic.

Role of bone morphogenetic proteins in periodontal tissue engineering: Relatively unexplored horizon

Tissue engineering aims to reconstruct the natural target tissue by a combination of three key elements stem/progenitor cells (that will create the new tissue), signaling molecules (that instruct the cells to form the desired tissue) scaffold/extracellular matrix (to hold the cells). Regeneration of the periodontal tissues following destructive episodes of various forms of periodontitis is a formidable challenge to periodontologists. Bone morphogenic proteins have been considered as the most potent growth factors that can promote the bone regeneration. This review will emphasize on the unique nature of the tissue engineered bone morphogenic proteins molecules regarding their structure, classification, signaling mechanism, etc. which will further help in understanding their role and potential advances necessary to facilitate the process of regeneration in the field of periodontics.

Ni-Catalyzed Hydroarylation of Alkynes with Unactivated β-C(sp2)-H Bonds

Hydroarylation of alkynes with unactivated C(sp2)-H bonds via chelated C-H metalation mainly occurs at γ-position to the coordinating atom of directing groups via stable 5-membered metallacycles, while β-C(sp2)-H bond-involved hydroarylation has been a formidable challenge. Herein, we used a phosphine oxide-ligated Ni-Al bimetallic catalyst to enable β-C-H bond-involved hydroarylations of alkynes via a rare 7-membered nickelacycle.

Rapid meniscus-guided printing of stable semi-solid-state liquid metal microgranular-particle for soft electronics

Liquid metal (LM) is being regarded as the most feasible material for soft electronics owing to its distinct combination of high conductivity comparable to that of metals and exceptional deformability derived from its liquid state. However, the applicability of LM is still limited due to the difficulty of achieving its mechanical stability and intrinsic conductivity. Furthermore, reliable and rapid patterning of stable LM directly on various soft substrates at high-resolution remains a formidable challenge. In this work, meniscus-guided printing of ink containing polyelectrolyte-attached LM microgranular-particle (PaLMP) in an aqueous solvent to generate semi-solid-state LM is presented. PaLMP printed in the evaporative regime is mechanically stable, intrinsically conductive, and patternable down to 50 µm on various substrates. Demonstrations of the ultrastretchable (~500% strain) electrical circuit, customized e-skin, and zero-waste ECG sensor validate the simplicity, versatility, and reliability of this manufacturing strategy, enabling broad utility in the development of advanced soft electronics.