Measurements Of Ep Research Articles

Measurement of the diffractive cross section and properties of the hadronic final state

Measurements of diffractive ep scattering performed by the ZEUS and H1 collaborations at HERA are presented. The diffractive cross section and the structure function F 2 D were measured and a model based on a partonic Pomeron structure was developed. Properties of the hadronic final state in terms of global event shape variables, dijet cross sections and energy flows were studied by both experiments and compared to predictions of this model.

Observation of events at very high $Q^2$ in ep collisions at HERA

Measurements of ep scattering with squared 4—momentum transfer Q2 up to 35000 GeV2 are compared with the expectation of the standard deep-inelastic model of lepton—nucleon scattering (DIS). For Q2 > 15000 GeV2, N obs = 12 neutral current candidate events are observed where the expectation is N DIS = 4.71 ± 0.76 events. In the same Q2 range, N obs = 4 charged current candidates are observed where the expectation is N DIS = 1.77 ± 0.87 events. The probability P(N ≥ N obs) that the DIS model signal N fluctuates to N ≥ N obs in a random set of experiments is 6 × 10−3 for neutral current and 0.14 for charged current. The difference in the observed and expected number of Neutral Current events is mostly due to events at large masses $M = \sqrt {xs}$ in which the positron is backscattered at large y = Q2/M2.

Analysis of reaction time in post-acute schizophrenia using electrophysiologic variables

20 postacute schizophrenic patients with predominantly negative symptoms and 21 age and sex matched normal controls were investigated in a P300 paradigm with simultaneous measurement of EP, EMG and behavioural reaction time. The steps of central information processing were operationalized by the following measures: input processing time (IPT): N1-latency; central processing time (CPT): N1-latency until EMG-onset; motor execution time (MET): EMG-onset until onset of target behaviour. For the schizophrenic group we found a pattern of significant deviations with reduction of the N1-, N2- and P3-amplitude, prolongation of the central processing, motor execution and behavioural termination time. The largest loss of time however was found for the central information processing time (203.1 +/- 72.9 vs. 113.1 vs. 20.2 ms, p = 0.000). In the control group the EMG reaction started 12.4 ms before the N2 peak, in the schizophrenic group 63.5 ms after the N2 peak (p = 0.02). Summing up, these findings are compatible with the assumption of a multiple functional deficit of central information processing in schizophrenia.

Experimental studies of ischemia of the cochlea. Part 1: Method

For the etiology of certain inner ear diseases e.g. sudden hearing loss, an impaired cochlear blood flow is discussed. The model of the ferromagnetic thrombosis is an atraumatic method to produce a selective ischemia of the inner ear. The measurement of the inner ear potentials EP, MP and CAP can help to elucidate which inner ear structures are primarily impaired by local ischemia. During the action of a magnetic field to the right cochlea an intravenous injection of small iron particles leads to a thrombosis of the cochlear veins. EP, MP and CAP were measured in the thrombosed ear and MP and CAP in the undisturbed contralateral ear. The methods of microsurgery on the middle and inner ear, the electrophysiological measurement techniques of the inner ear potentials and the method of producing a ferromagnetic thrombosis are described in detail.

Comparison of unitages for total free erythrocyte protoporphyrin (total EP) in anemia screening

The presence of free protoporphyrin in erythrocytes was previously reported by Hymans van den Bergh and Hyman [l]. In addition, increased free erythrocyte protoporphyrin is often observed in some diseases [2]. In iron-deficiency anemia, free erythrocyte protoporphyrin also increases, because heme synthesis cannot be completed and a relative excess of the unused ‘free’ protoporphyrin accumulates in the erythrocytes [3]. Lamola and Yamane, however, reported that the fluorescent porphyrin in the erythrocytes of patients with lead intoxication or with iron-deficiency anemia is zinc protoporphyrin that easily dissociates into free protoporphyrin and zinc ions in acidic solvents [4]. In another report, Piomelli [5] developed a micromethod for free erythrocyte protoporphyrin determination in which protoporphyrin in erythrocytes is extracted with an acidic solvent then determined as a free type of protoporphyrin, therefore the method determines free and zinc protoporphyrin, the so-called total erythrocyte protoporphyrin (total EP). Since then, the measurement of total EP has been recognized as a sensitive indicator for lead intoxication in children and is a simple procedure for any clinical laboratory. The total EP can be determined and calculated as four different units: pg/dl-blood, pg/dl-packed cell volume (pcv), pg/g-heme and pg/g-hemoglobin (Hb). The aim of the present study is to detect which unit is the most useful to evaluate or screen for the presence anemia.

Intracellular microelectrode measurements in small cells evaluated with the patch clamp technique

Microelectrode penetration of small cells leads to a sustained depolarization of the resting membrane potential due to a transmembrane shunt resistance (Rs) introduced by the microelectrode. This has led to underestimation of the resting membrane potential of various cell types. However, measurement of the fast potential transient occurring within the first few milliseconds after microelectrode penetration can provide information about pre-impalement membrane electrophysiological properties. We have analyzed an equivalent circuit of a microelectrode measurement to establish the conditions under which the peak of the impalement transients (Ep) approaches the pre-impalement resting membrane potential (Em) of small cells most closely. The simulation studies showed that this is the case when the capacitance of the microelectrode is low and the membrane capacitance of the cell high. In experiments performed to assess the reliability of Ep as a measure of Em, whole-cell patch clamp measurements were performed in the current clamp mode to monitor, free from the effects of Rs, Em in cultured human monocytes. Microelectrode impalement of such patch clamped cells and measurement of Ep made it possible to detect correlation between Ep and Em and showed that for small cells such as human monocytes Ep is on average 6 mV less negative than the resting membrane potential.

EEG and multimodality EP measurements in comatose patients

EEG and multimodality EP measurements in comatose patients

ADP stimulates hydrolysis of the “ADP-insensitive” phosphoenzyme in Na+, K+-ATPase and Ca2+-ATPase.

ADP-sensitive (E1P) and K+-sensitive (E2P) phosphoenzymes are sequentially formed intermediates in the reaction pathways catalyzed by the Na+,K+- and Ca2+-ATPases. The kinetics of dephosphorylation of these intermediates were examined by means of rapid quenching with acid at 21 degrees C. Under conditions favoring the formation of E2P (25 mM Na+ and O K+), addition of 5 mM ADP + 10 mM EDTA to the Na+,K+-ATPase phosphoenzyme produced a biphasic pattern of dephosphorylation. Both phases of phosphoenzyme decomposition were accompanied by approximately stoichiometric amounts of inorganic phosphate (Pi) release. The rate of decay of the rapid phase was 10 times faster than the rate of phosphoenzyme turnover under phosphorylating conditions indicating acceleration of E2P hydrolysis by ADP. Similar patterns of ADP-stimulated phosphoenzyme decay and Pi release were observed in the Ca2+-ATPase from sarcoplasmic reticulum phosphorylated at low (0.1 mM) Mg2+ in the absence of KCl. These results demonstrate that ADP can enhance the rate of E2P hydrolysis in the cases of the Na+,K+-ATPase and Ca2+-ATPase. As a consequence measurement of "ADP-sensitive EP" may overestimate E1P.

Plasmon energy and chemical composition of amorphous SiX C1-X:H

Using a TEM equipped with an electron energy loss spectrometer (EELS) the plasmon energy, Ep of a material can easily be determined for specimens of thickness up to a few thousand Å. This coincides with the film thicknesses encountered in thin film technology, e.g., amorphous solar cells. Ep is to the first approximation proportional to the square root of the valence electron density, and is thus sensitive to the chemical composition and the density of a material. Ep measurements using EELS have therefore the potential of being a convenient way of characterizing a material, as has been demonstrated for hydrogenated metals, and this could be particularly useful for amorphous materials where characterization techniques such as x-ray and electron diffraction are of limited value.

Polyhalogenoheterocyclic compounds—3 21: Radical-anions from halopyridines

Electrochemical reduction of pentafluoropyridine and other polyhalopyridines gives bipyridyl derivatives etc. and it is inferred from the structures of the products that, in the intermediate radical-anion, charge- and spin-density is concentrated at the 1- and 4-positions. This is further supported by measurement of Ep 1 2 values. Trapping experiments with hydroquinone and carbon dioxide are described.

Ipsilateral and contralateral correlations between EEG and EP principal components

Correlations between EP and EEG principal components are reported. The signs of the correlations appear to depend on 3 factors: frequency of the EEG, whether the EP and EEG were measured from ipsilateral or contralateral leads, and EP latency. Correlations are negative between EP amplitude (at 100–150 msec) and EEG alpha from ipsilateral leads contralateral to the EEG alpha measurements, the correlations are positive. EEG beta, however, shows the opposite pattern (ipsilateral correlations are positive, while contralateral correlations are negative). Finally, there is some indication of higher ipsilateral correlations for earlier EP components (as opposed to lower correlations for later EP components), and higher contralateral correlations for later EP components. The EPs and EEGs were taken during separate experimental conditions as part of the same experimental session. The original EP measurements were amplitudes (N100, P150, N200, and P300) to words flashed on a television screen, as S1 of a CNV paradigm. The EEGs were 4 sec epochs taken immediately upon television presentation of a word or picture problem.

Determination of [formula omitted] from η-electroproduction at the S 11(1535) resonance

We report on measurements of the reaction ep → epη in the region of the S 11(1535) resonance. The experiment was done at an invariant four-momentum transfer q 2 = 0.4 (GeV/ c) 2 at two different scattering angles for the outcoming electron ( θ e = 22° and 55°) in oder to separate the cross sectionsσ L and σ T. A value of 0.23 ± 0.11 was obtained for the ratio R = σ L σ T .

Inclusive Pion Electroproduction at LargepT

We report measurements of the inclusive electroproduction reaction ep..-->..e..pi../sup +/X for pions produced at 90degree in the virtual-photon-proton center-of-mass system. Data are presented at the (W,Q/sup 2/) points (2.2 GeV, 1.2 GeV/sup 2/), (2.2, 3.6), (2.65, 1.2), (2.65, 2.0), (2.65, 2.8), (2.65, 3.6), (3.1, 1.2), and (3.1, 2.0). The invariant structure function is studied as a function of W, Q/sup 2/, x/sub T/, p/sub T//sup 2/, and the square of the invariant undetected mass. (AIP)

Determination of the nucleon axial vector form-factor from πΔ electroproduction near threshold

From measurements of the reaction ep→e π − Δ ++ near threshold the nucleon axial-vector form factor is determined, using the PCAC calculations by Adler and Weisberger. The results are consistent with form factor determinations from single pion electroproduction. A dipole fit yields m A = (1.18 ± 0.07) GeV.

Separation of σ S and σ T in the region of the Δ (1236) resonance and determination of the magnetic dipole transition form factor

The longitudinal and transverse cross sections σ S and σ T are evaluated from measurements of inelastic ep scattering at scattering angles ranging from 20° to 81°. The magnetic dipole transition from factor G ∗ M is determined and the reliability of the determination is discussed.