Gallium arsenide molecular beam epitaxy: Low temperature and surfactant-mediated

The reflection high-energy electron diffraction (RHEED) specular spot intensity oscillations that were obtained during low-temperature regime and surfactant mediated regime of molecular beam epitaxial (MBE) growth of GaAs is studied and explained using modified stochastic model and a rate equation model, respectively; The dynamics of the physisorbed As layer were introduced into the stochastic model by including the thermally activated processes of chemisorption into and evaporation out of the As physisorbed state. Increased scattering of the RHEED beam due to the higher physisorbed As coverage at 2:1 leads to a factor of 5 decrease in the steady-state amplitude of the RHEED oscillations compared to the 1:1 case. These results are in excellent agreement with the experimental results. A factor in maintaining this growth mode is that arsenic stays in the physisorbed state with lifetimes in the range of 10{dollar}\sp{-3}{dollar} to 10{dollar}\sp{-5}{dollar} seconds and incorporates only when an appropriate configuration of Ga atoms forms on the surface; Beating in the reflection high energy electron diffraction (RHEED) intensity oscillations were observed during molecular beam epitaxial (MBE) growth of GaAs with Sn as a surfactant. A rate equation model of growth was developed to explain this phenomenon by assuming that the GaAs covered by the Sn grows at a faster rate compared to the GaAs not covered by Sn. Assuming that the electron beams reflected from the Sn covered surface and the rest of the surface are incoherent, the results of the dependence of the RHEED oscillations on Sn submonolayer coverages for various Sn coverages were obtained and compared with experimental data and the qualitative agreement is very good. (Abstract shortened by UMI.)

Yield Enhancement of Digital Microfluidics-Based Biochips Using Space Redundancy and Local Reconfiguration

As microfluidics-based biochips become more complex, manufacturing yield will have significant influence on production volume and product cost. We propose an interstitial redundancy approach to enhance the yield of biochips that are based on droplet-based microfluidics. In this design method, spare cells are placed in the interstitial sites within the microfluidic array, and they replace neighboring faulty cells via local reconfiguration. The proposed design method is evaluated using a set of concurrent real-life bioassays.Comment: Submitted on behalf of EDAA (http://www.edaa.com/

Investigation of Heat Transfer Enhancement in Conceptual Two-pass Channels for Gas Turbine Internal Cooling

Modern gas turbines operate at high inlet temperatures due to which various components undergo severe thermal and mechanical stresses and fatigue. Suitable materials for withstanding such severe conditions are not available or are too expensive to manufacture. As a consequence, components need to be cooled to sustainable temperatures and efficient cooling strategies need to be developed. This study presents new internal cooling designs for turbine blades that eliminate the need for rib turbulators in internal passages producing significantly higher heat transfer enhancements. Detailed local heat transfer coefficient data of the proposed new designs (swirl generation using tangentially injected coolant from one pass to the second in serpentine coolant channels) are presented in this study. A transient liquid crystal technique involving a single color capturing method was employed in this study. Liquid crystals techniques are versatile and can be used for testing complex geometries. Also gas turbine internal coolant channels are typically tapered from hub to tip. Results are also presented for a tapered two-pass channel to compare and validate the assumption neglecting the effects of taper and using the local straight, two-pass channel data, for typically tapered internal coolant channels

Examining Mechanisms Regulating Microtubule Assembly and Function

Microtubules are cytoskeletal polymers assembled from α and β tubulin subunits that function in essentially all cellular activities. Microtubules can act as “tracks” for intracellular cargo transport, are required for cilia- and flagella-based motility, and establish cell morphology in specialized cells such as neurons. In dividing cells, a bipolar spindle assembles from microtubules and partitions genetic material into two daughter cells. Proper microtubule function in these diverse contexts depends on the assembly dynamics of microtubules and their organization into specialized arrays. Both intrinsic factors including the tubulin isotype composition of microtubules and extrinsic factors including microtubule-associated proteins (MAPs) can impact microtubule assembly dynamics. However, the contribution of tubulin isotype composition to microtubule dynamics is not well understood. In the first part of this thesis, I explore the impact of specific β tubulin isotypes on microtubule dynamics. Microtubules undergo dynamic instability, an intrinsic property in which filaments in bulk equilibrium switch between periods of growth and shrinkage. The rate of polymerization and depolymerization can be quantified, as well as the frequency of switching between these states. I selected the two major β tubulin isotypes (βIIB and βIII) expressed in the vertebrate brain for examination. Using an expression and purification system developed in our lab, I generated recombinant tubulin heterodimers that were isotypically pure in β tubulin composition. I used in vitro reconstitution and total internal reflection fluorescence (TIRF) microscopy to examine the dynamics of individual microtubules assembled from these distinct heterodimers. I found that microtubules assembled with βIIB are substantially more stable, switching from a state of growth to a state of shrinkage (termed catastrophe) three-fold less frequently than their βIII-containing counterparts. These two isotypes differ substantially in the C-terminal tail, a region thought important for modulating interactions with MAPs but whose contribution to microtubule dynamics is not well understood. I found that swapping the C-terminal tails did not substantially alter dynamic instability parameters. These data reveal that isotype-specific polymerization properties are mediated by residue changes in the structured “core” of tubulin, rather than the divergent C-terminal tail. In the second part of the thesis, I examine the contribution of microtubule bundles to chromosome movement during anaphase. As sister chromosomes separate, a specialized array of microtubules called the spindle midzone assembles between the segregating chromosomes. Within this structure, microtubules overlap in the antiparallel orientation and are cross-linked by the non-motor MAP, Protein Regulator of Cytokinesis 1 (PRC1), forming bundles. Current models suggest that the spindle midzone can function to facilitate or restrict chromosome movement, however it is unclear how the accumulation of PRC1 on midzone microtubule bundles impact these activities. Using lattice light sheet microscopy, I examined the time-dependent changes in microtubule overlap length that accompany anaphase chromosome movement. I then selectively disrupted midzone formation by knocking down PRC1 and found that chromosome segregation distance and speed increased. These data support a model in which the spindle midzone, rather than aiding in chromosome segregation, instead restricts chromosome movement. Replacing endogenous PRC1 with a mutant that has reduced microtubule affinity reveals that the change in microtubule overlap length is coupled to the braking function of the midzone. My PhD work provides insight into two areas of microtubule assembly regulation. The studies detailed in chapters 2 and 3 reveal how changes in tubulin primary sequence impact polymerization properties of microtubules in vitro. The studies detailed in chapter 4 reveal how changes in the organization of microtubules in cells contributes to spindle function and chromosome segregation during anaphase

Adsorption and Microfiltration Processes to Treat Dye and Coffee Wastewater.

Wastewater from coffee processing industry creates high biological and chemical oxygen demand in the surface water. In addition to coffee wastewater from coffee industry, dyes from textile industry enter surface water affecting water quality in terms of transmissivity of light. Adsorption is an economical wastewater treatment process to remove color from dye and coffee wastewater. In the current thesis, adsorption using low-cost adsorbents like peanut hull and onion peel are used to treat combined dye and coffee wastewater. Three representative dyes including acid black 48, disperse yellow 3, crystal violet certified with processed coffee is used in preparing batch adsorption samples. Using UV-Vis Spectrophotometer, absorbance and transmittance of the wastewater samples are measured. After adsorbents reach adsorption capacity, the suspended solids are removed using Whatman 41 microfilters. To understand the change in organic carbon before and after treatment in the wastewater, NPOC (Non-Purgeable Organic Carbon) is compared using Shimadzu TOC analyzer. This thesis focuses on the two-stage treatment process of adsorption and microfiltration in a binary mixture of dye and coffee wastewater. Increasing Adsorbent dosage in the representative wastewater samples gives us the idea of optimum dosage required in the treatment process. The comparative study of adsorbent dosage with transmittance and NPOC gives us an understanding of the efficiency of low-cost adsorbents when compared to Powdered Activated Carbon

Pseudo SS-spectra of special operators in quaternionic Hilbert spaces

For a bounded quaternionic operator $T$ on a right quaternionic Hilbert space $\mathcal{H}$ and $\varepsilon >0$, the pseudo $S$-spectrum of $T$ is defined as \begin{align*} \Lambda_{\varepsilon}^{S}(T) := \sigma_S (T) \bigcup \left \{ q \in \mathbb{H}\setminus \sigma_S(T):\; \|\Delta_{q}(T)^{-1}\| \geq \frac{1}{\varepsilon} \right\}, \end{align*} where $\mathbb{H}$ denotes the division ring of quaternions, $\sigma_S(T)$ is the $S$-spectrum of $T$ and $\Delta_q(T)= T^2-2 \text{Re}(q)T+|q|^2I$. This is a natural generalization of pseudospectrum from the theory of complex Hilbert spaces. In this article, we investigate several properties of the pseudo $S$-spectrum and explicitly compute the pseudo $S$-spectra for some special classes of operators such as upper triangular matrices, self adjoint-operators, normal operators and orthogonal projections. In particular, by an application of $S$-functional calculus, we show that a quaternionic operator is a left multiplication operator induced by a real number $r$ if and only if for every $\varepsilon>0$ the pseudo $S$-spectrum of the operator is the circularization of a closed disc in the complex plane centered at $r$ with the radius $\sqrt{\varepsilon}$. Further, we propose a $G_1$-condition for quaternionic operators and prove some results in this setting.Comment: 21 pages, 3 figures; few references added. Some typos fixed. To appear in Linear Algebra and its Application

PkM Peningkatan Produksi Bawang Goreng di UMKM SLB Samala Nerugrasha 1 Kunir Lumajang

SLB Samala Nerugrasa 1 Kunir opened a small business as a learning place for students with special needs or disabilities who are not easy to get a job directly. However, the production process and knowledge management are not yet optimal. Thus, the aim of the program is to increase fried onion production through training and mentoring as well as updating technologies in these small businesses. The method uses the ABCD approach with five stages. The results of the first phase found that this SLB has assets in the form of complete fried onion production equipment but the condition of the equipment is still manual. The second stage found that his hopes and wishes were that fried onions could be produced every day and the income from selling fried onions was to improve learning facilities at SLB Samala in urder to the graduates will be easy to find jobs after graduated. The third stage, teachers in special schools are encouraged to participate in all activities so that they can impart their knowledge to other teachers and students. The fourth stage, the training carried out was MSME management, food preservation, packaging, and technology renewal. The final stage is that the training is carried out directly and indirectly. Finally, the SLB Samala began to be able to organize his business management and his products were better known for their quality