Tunneling and nonlinear transport in a vertically coupled GaAs/AlGaAs double quantum wire system

We report low-dimensional tunneling in an independently contacted vertically coupled quantum wire system. This nanostructure is fabricated in a high quality GaAs/AlGaAs parallel double quantum well heterostructure. Using a novel flip chip technique to align top and bottom split gates to form low-dimensional constrictions in each of the independently contacted quantum wells we explicitly control the subband occupation of the individual wires. In addition to the expected 2D-2D tunneling results, we have found additional tunneling features that are related to the 1D quantum wires.Comment: 4 pages, 3 figures, submitted to APL Minor revision

Undoped Electron-Hole Bilayers in a GaAs/AlGaAs Double Quantum Well

We present the fabrication details of completely undoped electron-hole bilayer devices in a GaAs/AlGaAs double quantum well heterostructure with a 30 nm barrier. These devices have independently tunable densities of the two-dimensional electron gas and two-dimensional hole gas. We report four-terminal transport measurements of the independently contacted electron and hole layers with balanced densities from $1.2 \times 10^{11}$cm$^{-2}$ down to $4 \times 10^{10}$ cm$^{-2}$ at $T = 300 mK$. The mobilities can exceed $1 \times 10^{6}$ cm$^{2}$ V$^{-1}$ s$^{-1}$ for electrons and $4 \times 10^{5}$ cm$^{2}$ V$^{-1}$ s$^{-1}$ for holes.Comment: 3 pages, 3 figure

Coulomb Drag in the Exciton Regime in Electron-Hole Bilayers

We report electrical transport measurements on GaAs/AlGaAs based electron-hole bilayers. These systems are expected to make a transition from a pair of weakly coupled two-dimensional systems to a strongly coupled exciton system as the barrier between the layers is reduced. Once excitons form, phenomena such as Bose-Einstein condensation of excitons could be observed. In our devices, electrons and holes are confined in double quantum wells, and carriers in the devices are induced with top and bottom gates leading to variable density in each layer. Separate contact to each layer allows Coulomb drag transport measurements where current is driven in one layer while voltage is measured in the other. Coulomb drag is sensitive to interlayer coupling and has been predicted to provide a strong signature of exciton condensation. Drag measurement on EHBLs with a 30 nm barrier are consistent with drag between two weakly coupled 2D Fermi systems where the drag decreases as the temperature is reduced. When the barrier is reduced to 20 nm, we observe a consistent increase in the drag resistance as the temperature is reduced. These results indicate the onset of a much stronger coupling between the electrons and holes which leads to exciton formation and possibly phenomena related to exciton condensation.Comment: 12 pages, 3 figure

Hysteresis in the quantum Hall regimes in electron double quantum well structures

We present in this paper experimental results on the transport hysteresis in electron double quantum well structures. Exploring the measurement technique of fixing the magnetic field and sweeping a front gate voltage (Vg), we are able to study the hysteresis by varying the top layer Landau level fillings while maintaining a relatively constant filling factor in the bottom layer, allowing us to tackle the question of the sign of Rxx(up)-Rxx(down), where Rxx(up) is the magnetoresistance when Vg is swept up and Rxx(down) when Vg swept down. Furthermore, we observe that hysteresis is generally stronger in the even integer quantum Hall effect (IQHE) regime than in the odd-IQHE regime. This, we argue, is due to a larger energy gap for an even-IQHE state, determined by the Landau level separation, than that for an odd-IQHE state, determined by the Zeeman splitting

Photoluminescence Detected Doublet Structure in the Integer and Fractional Quantum Hall Regime

We present here the results of polarized magneto-photoluminescence measurements on a high mobility single-heterojunction. The presence of a doublet structure over a large magnetic field range (2>nu>1/6) is interpreted as possible evidence for the existence of a magneto-roton minima of the charged density waves. This is understood as an indication of strong electronic correlation even in the case of the IQHE limit.Comment: submitted to Solid State Communication

Modified Periodic Acid-Schiff (PAS) Is an Alternative to Safranin O for Discriminating Bone–Cartilage Interfaces

Cartilage histomorphometry is often performed on decalcified, paraffin-embedded bone sections, which provide versatility in staining applications from basic morphology to immunohistochemistry. Safranin O is a cationic dye that binds to proteoglycans in cartilage and is routinely used to assess growth plate dynamics and/or fracture repair at bone–cartilage interfaces. When used with a counterstain such as fast green, safranin O can offer exquisite differentiation of cartilage from surrounding bone. However, various decalcification and processing methods can deplete proteoglycans, rendering inconsistent, weak, or absent safranin O staining with indiscriminate bone–cartilage boundaries. We sought to develop an alternative staining methodology that preserves the contrast of bone and cartilage in cases of proteoglycan depletion that can be applied when other cartilage stains are unsuccessful. Here, we describe and validate a modified periodic acid-Schiff (PAS) protocol that we developed using Weigert\u27s iron hematoxylin and light green stains as an alternative to safranin O for discriminating bone–cartilage interfaces of skeletal tissues. This method provides a practical solution for differentiating bone and cartilage when safranin O staining is not detected after decalcification and paraffin processing. The modified PAS protocol can be useful for studies in which identification of the bone–cartilage interface is essential but may not be preserved with standard staining approaches

Uji Toksisitas Ginseng Kiyanpi Pada Benih Ikan Gurami (Osphronemus Goramy Lac)

Tujuan dari penelitian ini adalah untuk mendapatkan nilai LC50 ginseng kiyanpi pada benih ikan gurami. Penelitian ini dilaksanakan mulai bulan Juli 2016. Penelitian ini dilaksanakan di Jln. Merdeka No.708 RT 008 Kel. Talang semut Kec. Bukit Kecil Palembang. Metode penelitian ini menggunakan Rancangan Acak Lengkap (RAL), terdiri dari 1 kontrol, 5 taraf perlakuan dan 3 kali ulangan. Hasil penelitian ini menunjukan bahwa semakin tinggi konsentrasi ginseng kiyanpi maka semakin banyak hewan uji yang mati dengan kematian hingga 100 % sudah dapat dicapai pada perlakuan P5 dengan 0,50 g/20 g dan kematian terendah 10% terjadi pada perlakuan P1 dengan 0,10 g/20 g sedangkan pada perlakuan kontrol 0 g/20 g tidak terjadi kematian dan nilai LC50 96 jam diperoleh nilai tengah sebesar 0,30 g/20 g. Nilai kualitas air tiap perlakuan yaitu suhu berkisar antara 25-260 C dan pH 6,0-7,0 masih dalam batas toleransi untuk tumbuh kembang benih Ikan gurami. Kata Kunci : Gurami, Ginseng Kiyanpi, LC50 96 Jam, Kelangsungan Hidup, Mortalitas