Direct observation of nucleation and early stages of growth of GaN nanowires

We report direct observations of the nucleation and early stages of growth of GaN nanowires. The nanowires were formed by exposing Au+Ga droplets to ammonia. The formation process was observed in situ, and controlled in real time using an environmental transmission electron microscope. Observations show that nuclei forms only at thin region of the Au+Ga, following only the VLS mechanism. The droplet–nanowire interface in the initial stages is multi-faceted, and become planar during the growth. Chemical and structural analysis shows that the resulting nuclei are GaN with the wurtzite structure.     

In vivo and in vitro study of porcine oviductal epithelial cells, cumulus oocyte complexes and granulosa cells: a scanning electron microscopy and inverted microscopy study

The morphology and structure of porcine oviductal epithelial cells (POEC), cumulus-oocyte complexes (COCs) and granulosa cells (GC) were investigated in vivo and in vitro conditions using scanning electron microscopy (SEM) and inverted microscopy. The POEC contained columnar ciliated cells and spherical shaped non-ciliated cells. Both non- and ciliated cells appeared either in groups or distributing among each other. However, the isolation of cells was observed after culture for 48 h. A total of 921 oocytes from 20 ovaries was isolated resulting in an average of 46 oocytes per ovary. They were round in shape, surrounded by zona pellucida with layers of cumulus cells ranging between 89.16 and 144.68 μm in size. As for COCs, they were classified into 4 types; intact-, multi-, partial-cumulus cell layers and completely denuded oocyte. Interestingly, changes in morphology of COCs with intact and multi-cumulus cell layers were observed in the in vitro study. The GCs in the follicular fluid were also round in shape and found as clusters. After culturing in in vitro for 48 h, no change in morphology was observed. The GC appeared in smaller clusters or were present as single cells and their sizes ranged from 6 to 8 μm. The results obtained from this study allow us to have a better understanding of the morphology and nature of cells under both in vivo and in vitro conditions. This information is also important for the study of their secretions and biochemical compositions, which is of great importance to the use of cells as feeder cells in in vitro fertilization in current studies.     

Low‐Temperature Growth of Carbon Nanotubes Catalyzed by Sodium‐Based Ingredients

Synthesis of low‐dimensional carbon nanomaterials such as carbon nanotubes (CNTs) is a key driver for achieving advances in energy storage, computing, and multifunctional composites, among other applications. Here, we report high‐yield thermal chemical vapor deposition (CVD) synthesis of CNTs catalyzed by reagent‐grade common sodium‐containing compounds, including NaCl, NaHCO₃, Na₂CO₃, and NaOH, found in table salt, baking soda, and detergents, respectively. Coupled with an oxidative dehydrogenation reaction to crack acetylene at reduced temperatures, Na‐based nanoparticles have been observed to catalyze CNT growth at temperatures below 400 °C. Ex situ and in situ transmission electron microscopy (TEM) reveal unique CNT morphologies and growth characteristics, including a vaporizing Na catalyst phenomenon that we leverage to create CNTs without residual catalyst particles for applications that require metal‐free CNTs. Na is shown to synthesize CNTs on numerous substrates, and as the first alkali group metal catalyst demonstrated for CNT growth, holds great promise for expanding the understanding of nanocarbon synthesis.     

Label-free and rapid spectroscopic evaluation of ripening of Syzygium cumini fruit

In the present investigation, attempts have been made to obtain the spectral signature of the fruit jamun and to estimate the changes in biochemical composition that take place in the process of ripening of the fruits. The changes in exocarp, mesocarp, and seed of the fruit in raw and ripe stages have been investigated with the help of label-free, nondestructive, and rapid techniques: laser-induced fluorescence and attenuated total reflectance Fourier transform infrared spectroscopy. For this, the fluorescence spectra of the different parts (exocarp, mesocarp, and seed) of the raw and ripe fruits of jamun excited by 405?nm violet diode laser have been recorded in the spectral region 400–900?nm. The spectrum shows the spectral signature of anthocyanin, flavonoids, carotenoid, and chlorophyll. The observed decrease in the intensity of chlorophyll bands and simultaneous increase in the intensity of anthocyanin and carotenoid bands is regarded as indicator of the ripening of the fruit of jamun. Also, attenuated total reflectance Fourier transform infrared spectra have been recorded in the spectral region 4000–485?cm^?1 for the identification of functional groups associated with different biochemical altered during ripening process of the fruits of jamun. The analyses of the recorded infrared spectra show the presence of carbohydrates, cell wall components, phenolic compounds, nucleic acid, and amide. The quantitative estimation of the biochemical content in the different parts of jamun fruit during the ripening process has been done through calculating the area of the band by curve fitting. The determined spectral signatures can be utilized for the effective monitoring of jamun fruit.     

Thiosugars Iii. Stereoselective Approach to β-(1→2)-2,3-Dideoxy-2-C-Acetamidomethyl-2-S-Thiodisaccharides From Levoglucosenone

ABSTRACT

β-(1→2)-2,3-Dideoxy-2-C-acetamidomethyl-2-S-thiodisaccharides were synthesized in four steps by a stereoselective base catalyzed Michael addition reaction of 1-thiosugars to α-nitroalkene 4a, a new chiral synthon from levoglucosenone. It was followed by the reduction of the nitro group with a sodium borohydride/cobalt chloride complex and the hydrolytic opening of the 1,6-anhydro ring.     

Finite nets of dimension d

This paper introduces the concept of a finite net of dimension d. This is a generalization of the finite net of dimension three, due to Laskar and the finite net (of dimension two) due to Bruck. An association scheme is defined on this system which is then shown to form a partially balanced incomplete block design on an association scheme with d associate classes.     

On powers and centers of chordal graphs

A graph is chordal if every cycle of length strictly greater than three has a chord. A necessary and sufficient condition is given for all powers of a chordal graph to be chordal. In addition, it is shown that for connected chordal graphs the center (the set of all vertices with minimum eccentricity) always induces a connected subgraph. A relationship between the radius and diameter of chordal graphs is also established.     

On pseudo-Goldstone boson masses from broken gauge interactions

We investigate the effects of extended technicolour interactions on the masses of pseudo-Goldstone bosons in one-technifamily models. We find that the P⁰ and P³ cannot acquire any masses from ETC, while the P^± only acquire contributions of order g_Wg_ETC (?5 GeV). This removes a major source of uncertainty in the masses of these particles.