Light effective hole mass in undoped Ge/SiGe quantum wells

We report density-dependent effective hole mass measurements in undoped germanium quantum wells. We are able to span a large range of densities ($2.0-11\times10^{11}$ cm$^{-2}$) in top-gated field effect transistors by positioning the strained buried Ge channel at different depths of 12 and 44 nm from the surface. From the thermal damping of the amplitude of Shubnikov-de Haas oscillations, we measure a light mass of $0.061m_e$ at a density of $2.2\times10^{11}$ cm$^{-2}$. We confirm the theoretically predicted dependence of increasing mass with density and by extrapolation we find an effective mass of $\sim0.05m_e$ at zero density, the lightest effective mass for a planar platform that demonstrated spin qubits in quantum dots

The Essential Order of (L_p,p

درسنا في هذا البحث درجة التقريب الاساسي بأستخدام الشبكة العصبية المنتظمة ، وكيف يمكن تقريب الدوال  المتعددة المتغيرات في فضاء  عندما  بأستخدام الشبكة العصبية الامامية المنتظمة ، وكذلك بامكاننا الحصول على مبرهنات مباشرة وعكسية ونظرية تكافؤ للتقريب المتعددة المتغيرات في فضاء  عندما  بأستخدام الشبكة العصبية الامامية المنتظمة .This paper is concerning with essential degree of approximation using regular neural networks and how a multivariate function in  spaces for  can be approximated using a forward regular neural network. So, we can have the essential approximation ability of a multivariate function in  spaces for  using regular FFN

Strong spin-photon coupling in silicon

We report the strong coupling of a single electron spin and a single microwave photon. The electron spin is trapped in a silicon double quantum dot and the microwave photon is stored in an on-chip high-impedance superconducting resonator. The electric field component of the cavity photon couples directly to the charge dipole of the electron in the double dot, and indirectly to the electron spin, through a strong local magnetic field gradient from a nearby micromagnet. This result opens the way to the realization of large networks of quantum dot based spin qubit registers, removing a major roadblock to scalable quantum computing with spin qubits

Vascular Endothelial Cell Growth Factor Expression In Endothelial Cells Is Induced By Mechanical Wounding

Endothelial cell motility is central to several biological processes including angiogenesis during wound healing, reendothelialization of vessel walls after damage and neovascularization of tumors. However, control mechanisms that stimulate and inhibit cell movement are not known. Our objective is to understand the signals that initiate movement of endothelial cells. To examine these questions, we used an in vitro wound model of quiescent pulmonary artery endothelial cell monolayers which were stimulated to move by mechanical injury. Ca2+ signaling at the time of wounding produces long lasting effects on cell movement. We investigated whether new gene transcription after wounding might also stimulate endothelial cell movement. Specifically, we examined transcriptional activation of vascular endothelial cell growth factor (VEGF) after injury. While many studies have reported that tumor and epithelial cells produce VEGF, there is conflicting evidence for VEGF synthesis by endothelial cells. We found that RNA transcripts for 121 and 165 amino acids VEGF isoforms were expressed in quiescent endothelial cells. These transcripts were also produced by ovarian cancer cells which induce angiogenesis in vivo. Surprisingly, after wounding, additional RNA transcripts encoding the 189 amino acid VEGF isoform were induced. VEGF might self-stimulate endothelial cells since exogenous, recombinant VEGF accelerated cell motility as much as basic fibroblast growth factor. Our data suggest that expression of the 189 amino acid VEGF isoform is upregulated in response to extravascular signals such as mechanical wounding. VEGF might act in an autocrine or paracrine manner to stimulate movement after wounding

The Effects of Preeclampsia On The Enzymatic Activity Of Full Term Placentae:Histochemical Study

Background: This study is concerned with the effects of preeclampsia on the availability of the important enzymes in the full term placenta.For this purpose 2 groups of placentae were taken from the full term pregnant women immediately after labour, each group consists of 10 placentae, the first group are those placentae obtained from pregnant women having uneventful pregnancy with no history of any disease or complication (as a control group) while the second group includes those pregnant women having a history of preeclampsia, the results showed significant histochemical changes in the placentae of the second group when compared with the first group, such changes result from syncytial damage and destruction affecting the preeclamptic placentae of the second group, thus loss of alkaline phosphatase enzyme with increase in the amount of the degenerating acid phosphatase enzyme were observed in the placentae obtained from the preeclamptic group. the placentae have been implicated in the pathophysiology of preeclampsia.  Patients & Methods: The specimens were obtained from Al-Batool & Al-Khansaa Teaching Hospital in Mosul between February and July (2006) and studied in the Department of Anatomy, College of Medicine,University of Mosul. Two groups of placentae were taken from the full tem pregnant women immediately after labour, each group consists of 10 placentae, the first group was obtained from healthy pregnant women (control group) while the second group was obtained from pregnant women with history of preeclampsia (10 patients). Results: the placental alkaline phosphatase enzyme is very important in trophoblastic transfer mechanism, this enzyme is abundant at term normal placenta. The human placenta contains this enzyme which is produced mainly by syncytiotropholast cells thus destruction of these cells which occurs in preeclampsia will lead to decrease in this enzyme activity and increase in degenerating acid phosphatase enzyme activity. Conclusion: there is a disturbance in the level of acid and alkaline phosphatase enzymes in the preeclamptic full term placentae

Low disordered, stable, and shallow germanium quantum wells: a playground for spin and hybrid quantum technology

Buried-channel semiconductor heterostructures are an archetype material platform to fabricate gated semiconductor quantum devices. Sharp confinement potential is obtained by positioning the channel near the surface, however nearby surface states degrade the electrical properties of the starting material. In this paper we demonstrate a two-dimensional hole gas of high mobility ($5\times 10^{5}$ cm$^2$/Vs) in a very shallow strained germanium channel, which is located only 22 nm below the surface. This high mobility leads to mean free paths $\approx6 \mu m$, setting new benchmarks for holes in shallow FET devices. Carriers are confined in an undoped Ge/SiGe heterostructure with reduced background contamination, sharp interfaces, and high uniformity. The top-gate of a dopant-less field effect transistor controls the carrier density in the channel. The high mobility, along with a percolation density of $1.2\times 10^{11}\text{ cm}^{-2}$, light effective mass (0.09 m$_e$), and high g-factor (up to $7$) highlight the potential of undoped Ge/SiGe as a low-disorder material platform for hybrid quantum technologies

Co-occurrence of the Cyanotoxins BMAA, DABA and Anatoxin-a in Nebraska Reservoirs, Fish, and Aquatic Plants

Several groups of microorganisms are capable of producing toxins in aquatic environments. Cyanobacteria are prevalent blue green algae in freshwater systems, and many species produce cyanotoxins which include a variety of chemical irritants, hepatotoxins and neurotoxins. Production and occurrence of potent neurotoxic cyanotoxins β-N-methylamino-L-alanine (BMAA), 2,4-diaminobutyric acid dihydrochloride (DABA), and anatoxin-a are especially critical with environmental implications to public and animal health. Biomagnification, though not well understood in aquatic systems, is potentially relevant to both human and animal health effects. Because little is known regarding their presence in fresh water, we investigated the occurrence and potential for bioaccumulation of cyanotoxins in several Nebraska reservoirs. Collection and analysis of 387 environmental and biological samples (water, fish, and aquatic plant) provided a snapshot of their occurrence. A sensitive detection method was developed using solid phase extraction (SPE) in combination with high pressure liquid chromatography-fluorescence detection (HPLC/FD) with confirmation by liquid chromatography-tandem mass spectrometry (LC/MS/MS). HPLC/FD detection limits ranged from 5 to 7 μg/L and LC/MS/MS detection limits were \u3c0.5 μg/L, while detection limits for biological samples were in the range of 0.8–3.2 ng/g depending on the matrix. Based on these methods, measurable levels of these neurotoxic compounds were detected in approximately 25% of the samples, with detections of BMAA in about 18.1%, DABA in 17.1%, and anatoxin-a in 11.9%

Lightly-strained germanium quantum wells with hole mobility exceeding one million

We demonstrate that a lightly-strained germanium channel ($\varepsilon_{//}$ = -0.41%) in an undoped Ge/Si$_{0.1}$Ge$_{0.9}$ heterostructure field effect transistor supports a 2D hole gas with mobility in excess of 1$\times$10$^{6}$ cm$^{2}$/Vs and percolation density less than 5$\times$10$^{10}$ cm$^{-2}$. This low disorder 2D hole system shows tunable fractional quantum Hall effect at low density and low magnetic field. The low-disorder and small effective mass (0.068$m_e$) defines lightly-strained germanium as a basis to tune the strength of the spin-orbit coupling for fast and coherent quantum hardware