Inflammatory bowel diseases (IBDs) result in diarrhea and abdominal pain with further potential complications such as tissue fibrosis and stenosis. Animal models help in understanding the immunopathogenesis of IBDs and in the design of novel therapeutic concepts. Here we present an updated version of a protocol we published in 2007 for key models of acute and chronic forms of colitis induced by 2,4,6-trinitro-benzene sulfonic acid (TNBS), oxazolone and dextran sulfate sodium (DSS). This protocol update describes an adaptation of the existing protocol that modifies the technique. This protocol has been used to generate improved mouse models that better reflect the nature of IBDs in humans. In TNBS and oxazolone colitis models, topical administration of hapten reagents results in T-cell-mediated immunity against haptenized proteins and luminal antigens. By contrast, to generate DSS colitis models, mice orally receive DSS, causing death of epithelial cells, compromising barrier function and causing subsequent inflammation. The analysis of the acute colitis models can be performed within 1-2 weeks, whereas that of the chronic models may take 2-4 months. The strengths of the acute models are that they are based on the analysis of short-lasting barrier alterations, innate immune effects and flares. The advantages of the chronic models are that they may offer better insight into adaptive immunity and complications such as neoplasia and tissue fibrosis. The protocol requires basic skills in laboratory animal research.

We demonstrate theoretically that the shot noise produced by a tunnel barrier in a two-channel conductor violates a Bell inequality. The nonlocality is shown to originate from entangled electron-hole pairs created by tunneling events-without requiring electron-electron interactions. The degree of entanglement (concurrence) equals 2(T1T2)(1/2)(T1+T2)(-1), with T1,T2<<1 the transmission eigenvalues. A pair of edge channels in the quantum Hall effect is proposed as an experimental realization.

It is known that a quantum computer operating on electron-spin qubits with single-electron Hamiltonians and assisted by single-spin measurements can be simulated efficiently on a classical computer. We show that the exponential speed-up of quantum algorithms is restored if single-charge measurements are added. These enable the construction of a cnot (controlled not) gate for free fermions, using only beam splitters and spin rotations. The gate is nearly deterministic if the charge detector counts the number of electrons in a mode, and fully deterministic if it only measures the parity of that number.PACS numbers: 03.67. Lx,03.67.Mn,05.30.Fk, Flying qubits transport quantum information between distant memory nodes and form an essential ingredient of a scalable quantum computer [1]. Flying qubits could be photons [2], but using conduction electrons in the solid state for this purpose removes the need to convert material qubits to radiation. Since the Coulomb interaction between free electrons is strongly screened, an interaction-free mechanism for logical operations on electronic flying qubits could be desirable. The search for such a mechanism is strongly constrained by a no-go theorem [3,4], which states that the exponential speed-up of quantum over classical algorithms can not be reached with single-electron Hamiltonians assisted by single-spin measurements. Here we show that the full power of quantum computation is restored if single-charge measurements are added. These enable the construction of a cnot (controlled not) gate for free fermions, using only beam splitters and spin rotations.The no-go theorem [3,4] applies only to fermionsnot to bosons. Indeed, in an influential paper [2], Knill, Laflamme, and Milburn showed that the exponential speed-up over a classical algorithm afforded by quantum mechanics can be reached using only linear optics with single-photon detectors. The detectors interact with the qubits, providing the nonlinearity needed for the computation, but qubit-qubit interactions (e.g. nonlinear optical elements) are not required in the bosonic case. This difference between bosons and fermions explains why the topic of "free-electron quantum computation" (FEQC) is absent in the literature -in contrast to the active topic of "linear optics quantum computation" (LOQC) [5,6,7,8,9,10,11]. Here we would like to open up the former topic, by demonstrating how the constraint on the efficiency of quantum algorithms for free fermions can be removed. We accomplish this by using the fact * Permanent address: IBM, T.J. Watson Research Center, P.O. Box 218, Yorktown Heights, NY 10598, USA that the electron carrying the qubit in its spin degree of freedom has also a charge degree of freedom. Spin and charge commute, so a measurement of the charge leaves the spin qubit unaffected. To measure the charge the qubit should interact with a detector, but no qubit-qubit interactions are needed.Charge detectors play a prominent role in a variety of contexts: As which-path detectors they control the visibility of Ahar...

Signalling pathways determining the shear stress-induced production of NO from endothelial cells in situ were investigated using a bioassay system in which shear stress was increased by inducing vasoconstriction in an endothelium-intact donor segment (rabbit iliac artery) while maintaining a constant luminal perfusion rate. Shear stress-induced NO production, as assessed by changes in the tone of a preconstricted endothelium-denuded detector ring, was biphasic and consisted of an initial transient (20- to 25-minute) Ca(2+)-dependent phase followed by a Ca(2+)-independent plateau phase, which was maintained as long as the donor segment remained constricted. Stretching the donor segments to their in vivo length abolished the initial phase without affecting the plateau phase of NO release. Inhibition of the Na(+)-H+ exchanger using HOE 694 elicited an intracellular acidification which attenuated shear stress-induced NO production. The specific protein kinase C inhibitor, Ro 31-8220, was without effect, whereas the unspecific inhibitors, staurosporine and calphostin C, abolished the shear stress-induced production of NO. Erbstatin A, a tyrosine kinase inhibitor, attenuated the shear stress-induced tyrosine phosphorylation of specific cellular proteins and abrogated the associated NO production. In summary, these data indicate that shear stress activates the NO synthase at basal levels of [Ca2+]i via a mechanotransduction cascade that involves tyrosine phosphorylation and can be modulated by changes in pHi. The apparent fundamental alteration of the endothelial NO synthase under shear stress that renders its maintained activation independent of an increase in [Ca2+]i is probably the consequence of a change in the enzyme microenvironment.

The electronic capacitance of a one-dimensional system such as a carbon nanotube is a thermodynamic quantity that contains fundamental information about the ground state 1 . It is composed of an electrostatic component describing the interactions between electrons and their correlations, and a kinetic term given by the electronic density of states. Here, we use a field-effect transistor geometry to obtain the first direct capacitance measurement of individual carbon nanotubes, as a function of the carrier density. Our measurements detect the electrostatic part of the capacitance as well as the quantum corrections arising from the electronic density of states. We identify the van-Hove singularities that correspond to the onedimensional electron and hole sub-bands and show that the measured capacitance exhibits clear electron-hole symmetry. Finally, our measurements suggest the existence of a negative capacitance, which has recently been predicted to exist in one dimension as a result of interactions between electrons 2-4 . The capacitance of a classical conductor is determined solely by its geometry. When charged, the electrons distribute in space in a manner that minimizes their electrostatic energy. Quantum mechanics introduces extra energies that add new contributions to the capacitance. As the energies simply add and capacitance is inversely proportional to energy, these contributions add in series with the classical geometric capacitance (C g ) to yield the total capacitance, C −1xc . The first contribution is caused by the kinetic energy of the electrons. Adding electrons to a conductor requires finite kinetic energy and therefore adds a term (C dos ) that reduces the total capacitance. The second contribution results from the correlated motion of electrons, which generally leads to reduction of their total electrostatic energy 1,5,6 . This adds a negative capacitance term (C xc ) that increases the total capacitance. The density dependence of these terms captures the fundamental properties of the quantum ground state and their measurements in two-dimensional systems 7-11 established the role of interactions in the ground state.In one dimension, the capacitance plays a special role as it also determines the properties of the excitations. Described within the Luttinger model 12 , the fundamental excitations are collective waves of spin or charge. Electronic interactions lift the degeneracy of these modes by enhancing the velocity of the charge excitations by a factor g −1 , the inverse Luttinger parameter. This electrostatic effect is captured by the compressibility of the electronic gas 13 , or equivalently by its capacitance 2,14 . Thus, the central parameter of the Luttinger liquid theory is directly related to the capacitance by the simple relation g = √ C tot /C dos . So far, g has been inferred mostly from transport measurements [15][16][17][18][19][20] that probe the electronic excitations. Capacitance allows an independent thermodynamic determination of this parameter and its density dependence.In th...

We present here a quantum mechanical framework for defining the statistics of measurements of dtÂ(t), A(t) being a quantum mechanical variable. This is a generalization of the so-called full counting statistics proposed earlier for DC electric currents.We develop an influence functional formalism that allows us to study the quantum system along with the measuring device thus fully accounting for the action of the detector on the system to be measured. We define the full counting statistics of an arbitrary variable by means of an evolution operator that relates initial and final density matrices of the measuring device.In this way we are able to resolve inconsistencies that occur in earlier definitions. We suggest two schemes whereby the so defined full statistics can be observed experimentally.

In this article, we derive an effective theory of graphene on a hexagonal Boron Nitride (h-BN) substrate. We show that the h-BN substrate generically opens a spectral gap in graphene despite the lattice mismatch. The origin of that gap is particularly intuitive in the regime of strong coupling between graphene and its substrate, when the low-energy physics is determined by the topology of a network of zero energy modes. For twisted graphene bilayers, where inversion symmetry is present, this network percolates through the system and the spectrum is gapless. The breaking of that symmetry by h-BN causes the zero energy modes to close into rings. The eigenstates of these rings hybridize into flat bands with gaps in between. The size of this band gap can be tuned by a gate voltage and it can reach the order of magnitude needed to confine electrons at room temperature.

We report on a first-principles study of the conductance through graphene suspended between Al contacts as a function of junction length, width, and orientation. The charge transfer at the leads and into the freestanding section gives rise to an electron-hole asymmetry in the conductance and in sufficiently long junctions induces two conductance minima at the energies of the Dirac points for suspended and clamped regions, respectively. We obtain the potential profile along a junction caused by doping and provide parameters for effective model calculations of the junction conductance with weakly interacting metallic leads.