A Technique for High-Speed Microscopic Imaging of Dynamic Failure Events and Its Application to Shear Band Initiation in Polycarbonate

An experimental technique is reported, which can image the deformation fields associated with dynamic failure events at high spatial and temporal resolutions simultaneously. The technique is demonstrated at a spatial resolution of ~1 μm and a temporal resolution of 250 ns, while maintaining a relatively large field of view (≈ 1.11 mm × 0.63 mm). As a demonstration, the technique is used to image the deformation field near a notch tip during initiation of a shear instability in polycarbonate. An ordered array of 10 μm diameter speckles with 20 μm pitch, and deposited on the specimen surface near the notch tip helps track evolution of the deformation field. Experimental results show that the width of the shear band in polycarbonate is approximately 75 μm near the notch-tip within resolution limits of the experiments. The measurements also reveal formation of two incipient localization bands near the crack tip, one of which subsequently becomes the dominant band while the other is suppressed. Computational simulation of the experiment was conducted using a thermo-mechanically coupled rate-dependent constitutive model of polycarbonate to gain further insight into the experimental observations enabled by the combination of high spatial and temporal resolutions. The simulation results show reasonable agreement with the experimentally observed kinematic field and features near the notch-tip, while also pointing to the need for further refinement of constitutive models that are calibrated at high strain rates (~105/s) and also account for damage evolution.

The breeding biology of Fejervarya limnocharis complex, F. multistriata (Hallowell, 1861) in Mizoram, northeast India

The breeding behavior of Fejervarya multistriata was studied from the selected study sites in Mizoram for over three years between 2016 and 2019. In natural condition, breeding took place in group. The advertisement call of males consisted of a series of notes emitted at an interval of 0.1–0.4 s where the frequency spectra had a dominant band at 2670.1172 Hz and the band width ranges from 2497.8516–28422.3828 Hz. Morphometric measurements showed that females are larger than males with snout-vent length of 45.55 ± 1.54 mm vs 33.77 ± 1.03 mm, respectively. The clutch sizes ranges from 488 to 1035. We found that the calculated ‘t’ value 0.03 is less than the ‘p’ value, i.e. 1, therefore there is no correlation between SVL of females and clutch sizes.

Photoluminescence Characteristics of Zinc Blende InAs Nanowires

A detailed understanding of the optical properties of self-catalysed (SC), zinc blende (ZB) dominant, nanowires (NWs) is crucial for the development of functional and impurity-free nanodevices. Despite the fact that SC InAs NWs mostly crystallize in the WZ/ZB phase, there are very limited reports on the photoluminescence (PL) properties of ZB InAs NWs. Here, we report on the PL properties of Molecular Beam Epitaxy grown, SC InAs NWs. The as-grown NWs exhibit a dominant band to band (BtB) peak associated with ZB, InAs with an emission energy of ~0.41 eV in good agreement with the band gap energy of ZB InAs and significantly lower than that of the wurtzite phase (~0.48 eV). The strong BtB peak persists to near room temperature with a distinct temperature-dependent red-shift and very narrow spectral linewidth of ~20 meV (10 K) which is much smaller than previously reported values. A narrowing in PL linewidth with increasing NWs diameter is correlated with a decline in the influence of surface defects resulting from an enlargement in NWs diameter. This study demonstrates the high optical property of SC InAs NWs which is compatible with the Si-complementary metal-oxide-semiconductor technology and paves the way for the monolithic integration of InAs NWs with Si in novel nanodevices.

Lake-Effect Snowbands in Baroclinic Environments

Lake-effect snowstorms are often observed to manifest as dominant bands, commonly produce heavy localized snowfall, and may extend large distances inland, resulting in hazards and high societal impact. Some studies of dominant bands have documented concomitant environmental baroclinity (i.e., baroclinity occurring at a scale larger than the width of the parent lake), but the interaction of this baroclinity with the inland structure of dominant bands has been largely unexplored. In this study, the thermodynamic environment and thermodynamic and kinematic structure of simulated dominant bands are examined using WRF reanalyses at 3-km horizontal resolution and an innovative technique for selecting the most representative member from the WRF ensemble. Three reanalysis periods are selected from the Ontario Winter Lake-effect Systems (OWLeS) field campaign, encompassing 185 simulation hours, including 155 h in which dominant bands are identified. Environmental baroclinity is commonly observed during dominant-band periods and occurs in both the north–south and east–west directions. Sources of this baroclinity are identified and discussed. In addition, case studies are conducted for simulation hours featuring weak and strong along-band environmental baroclinity, resulting in weak and strong inland extent, respectively. These contrasting cases offer insight into one mechanism by which along-band environmental baroclinity can influence the inland structure and intensity of dominant bands: in the case with strong environmental baroclinity, inland portions of this band formed under weak instability and therefore exhibit slow overturning, enabling advection far inland under strong winds, whereas the nearshore portion forms under strong instability, and the enhanced overturning eventually leads to the demise of the inland portion of the band.

M918: A Novel Cell Penetrating Peptide for Effective Delivery of HIV-1 Nef and Hsp20-Nef Proteins into Eukaryotic Cell Lines

Background: HIV-1 Nef protein is a possible attractive target in the development of therapeutic HIV vaccines including protein-based vaccines. The most important disadvantage of protein-based vaccines is their low immunogenicity which can be improved by heat shock proteins (Hsps) as an immunomodulator, and cell-penetrating peptides (CPPs) as a carrier. Methods: In this study, the HIV-1 Nef and Hsp20-Nef proteins were generated in E.coli expression system for delivery into the HEK-293T mammalian cell line using a novel cell-penetrating peptide, M918, in a non-covalent fashion. The size, zeta potential and morphology of the peptide/protein complexes were studied by scanning electron microscopy (SEM) and Zeta sizer. The efficiency of Nef and Hsp20-Nef transfection using M918 was evaluated by western blotting in HEK-293T cell line. Results: The SEM data confirmed the formation of discrete nanoparticles with a diameter of approximately 200-250 nm and 50-80 nm for M918/Nef and M918/Hsp20-Nef, respectively. The dominant band of ~ 27 kDa and ~ 47 kDa was detected in the transfected cells with the Nef/ M918 and Hsp20-Nef/ M918 nanoparticles at a molar ratio of 1:20 using anti-HIV-1 Nef monoclonal antibody. These bands were not detected in the un-transfected and transfected cells with Nef or Hsp20- Nef protein alone indicating that M918 could increase the penetration of Nef and Hsp20-Nef proteins into the cells. Conclusion: These data suggest that M918 CPP can be used to enter HIV-1 Nef and Hsp20-Nef proteins inside mammalian cells efficiently as a promising approach in HIV-1 vaccine development.

Монодисперсные сферические наночастицы Gd-=SUB=-x-=/SUB=-Si-=SUB=-y-=/SUB=-O-=SUB=-z-=/SUB=- : Eu-=SUP=-3+-=/SUP=- для магнитно-резонансной томографии и оптической визуализации

The melt method is used for synthesizing monodispersed spherical silica nanoparticles Gd_ x -Si_ y O_ z :Eu^3+. The particle diameter is 450 nm, and the standard deviation does not exceed 5%. The nanoparticles have a line luminescence spectrum with a dominant band at 614 nm. The effect of a constant magnetic field up to 15 T on the intensity and shape of the luminescence spectra of Eu^3+ ions is studied. It is shown that the obtained material has a stable photoluminescence, the intensity of which does not depend on the magnetic field in the entire studied range. The synthesized nanoparticles Gd_ x Si_ y O_ z : Eu^3+ are promising for use as a contrast agent for magnetic resonance tomography and luminescent marker.

Heterologous Expression and Characterization of Thermostable Lipases from Geobacillus thermoleovorans PPD2 through Escherichia coli

ABSTRACT: Heterologous expression and purification of thermostable lipase from Geobacillus thermoleovorans PPD2 had been carried out through Escherichia coli BL21 as host. Two bands obtained showed lipolytic activity with the size at around 51 (LipA) and 43 (LipB) kDa, respectively. The activities were identified by zymogram analysis, while the control protein from Escherichia coli BL21(DE3) do not show any lipolytic activity. Purification of crude extract using chromatography affinity Ni-NTA resulted one dominant band of LipA, meanwhile LipB did not appeared on the gel. Another purification for LipB was carried out by acetone fractionation. Both of LipA and LipB showed high activity toward medium chain length substrates, with optimum activity at 50oC and pH 8.5. The activities of LipA and LipB showed tolerance toward short chain alcohols, such as methanol, ethanol, n-propanol, and isopropanol.

GAMMA-RAY BURST PROMPT EMISSION

The origin of gamma-ray burst (GRB) prompt emission, bursts of γ-rays lasting from shorter than one second to thousands of seconds, remains not fully understood after more than 40 years of observations. The uncertainties lie in several open questions in the GRB physics, including jet composition, energy dissipation mechanism, particle acceleration mechanism and radiation mechanism. Recent broad-band observations of prompt emission with Fermi sharpen the debates in these areas, which stimulated intense theoretical investigations invoking very different ideas. I will review these debates, and argue that the current data suggest the following picture: A quasi-thermal spectral component originating from the photosphere of the relativistic ejecta has been detected in some GRBs. Even though in some cases (e.g. GRB 090902B) this component dominates the spectrum, in most GRBs, this component either forms a sub-dominant "shoulder" spectral component in the low energy spectral regime of the more dominant "Band" component, or is not detectable at all. The main "Band" spectral component likely originates from the optically thin region due to synchrotron radiation. The diverse magnetization in the GRB central engine is likely the origin of the observed diverse prompt emission properties among bursts.

Development of Leukemia after HOXB4 Gene Transfer in the Canine Model.

HOXB4 is considered to be the only HOX gene that promotes self-renewal of hematopoietic stem cells without causing leukemia in mouse models. We investigated whether HOXB4 overexpression has similar effects in a clinically relevant canine model. A competitive repopulation assay was performed in three dogs in which CD34+ cells were transduced with MSCV-based gammaretroviral vectors expressing HOXB4GFP or control YFP. We observed up to 4-fold higher marking levels in granulocytes for the HOXB4GFP arm relative to the control 1 month after transplantation. The marking levels eventually decreased in all three animals and two dogs (G374, G450) have now been followed for more than 18 months. In G374, the marking levels for both arms stabilized at ~2% after 2 months post-transplantation. Between 14 and 20 months post-transplantation, the HOXB4GFP marking steadily increased to >95%, while YFP marking decreased to 0.1%. G374 was euthanized 21 months after transplantation due to declining health. Flow cytometry analysis showed that ~50% of BM cells expressed the monocyte marker CD14 and ~8% expressed the granulocyte marker DM5, all of which also expressed HOXB4GFP. CD3 and CD21 were expressed in 2% and 1% of cells, respectively, but these cells did not express HOXB4GFP. Bone marrow necropsy demonstrated significantly increased numbers of blast cells, consistent with a myelomonocytic leukemia. Southern blot analyses of G374 BM and PB samples identified 2 bands with the same intensity, suggesting a single dominant clone with 2 integration sites. LAM-PCR analysis identified two vector proviruses integrated ~100 kb upstream of c-myb, and into intron 3 of PRDM16. Western blot analysis confirmed expression of HOXB4 in cultured G374 BM cells but the levels of c-myb in these cells were not different from control HOXB4-transduced BM cells as determined by RT-PCR. The expression of PRDM16 exons 1–3 was not detected in cells from dog G374 or in control cells, however, PRDM16 exon 4 was expressed in G374 cells but not in control cells. RT-PCR using primers located in the MSCV LTR and in PRDM16 exon 4 identified a unique band and sequencing of this product showed that the 5′ LTR was spliced with PRDM16 exon 4 creating a short PRDM16 isoform which has been observed in human leukemias. These data suggest that HOXB4 overexpression in collaboration with integration-induced activation of PRDM16 led to the leukemia. Southern blot and SYBR green Q-PCR showed that the leukemic clone contributed to ~20% hematopoiesis in BM 6 months after transplantation, and gradually decreased to ~2% before final expansion of the clone, suggesting accumulation of other mutation(s) were required for overt leukemia. Karyotype analysis of BM cells has not shown any major abnormalities but we are currently performing analyses to search for minor abnormalities such as gene duplications and deletions. Recently, HOXB4GFP marking in dog G450 PB and BM has increased to 20% and 80%, respectively, while YFP marking has decreased to ~1%. Southern blot analysis has identified a single dominant band and a BM biopsy showed substantially increased blast cells. Of note, we have not observed leukemia in >30 dogs followed long term that received transduced cells without HOXB4. In summary, HOXB4 overexpression together with insertional mutagenesis by virus integration has induced leukemia in the canine model, demonstrating the utility of this model to study the safety of gene therapy.