Electronic conductivity of lead dioxide powder: separation of core and surface resistance of the particles

The electronic conductivity of active battery materials has seldom been investigated in detail. The problem is to separate the resistance contributions located in the particle cores and in the particle surfaces. In this paper battery PbO₂, the best-known model substance, has been studied.     

Ion uptake and growth of wheat seedlings treated with nitrite at different pH values

Increasing concentrations of NaNO2 caused decreases in the uptake of K+, Na+ and SO4(2-) by wheat roots at pH 4. At pH 6 or 7, the detrimental effect was much less. The translocation of nutrients to the shoots was also impaired. The root growth was strongly inhibited by increasing NaNO2 concentrations, but the shoot development was little affected. At low pH, however, the inhibitory effect was much higher.     

The New National Control Centre, Ireland

The new National Control Centre for the Electricity Supply Board (ESB), Ireland, currently undergoing site commissioning, will be in operation in September 1986. The Control Centre will control a single 2200 MW island network. The control centre is being supplied under a supply contract with Landis & Gyr, Zug, Switzerland. There is a high degree of customer participation and emphasis is laid on customer interfacing. The central hardware comprises a dual main 32-bit computer system with Virtual Memory Operating System, four dual front-end processors and four display processors. Remote Terminal Units communicate with the Control Centre on a private communication network, mostly Microwave and Power Line Carrier. This paper describes the control centre in a general way with emphasis on contractual arrangements, customer involvement and testing procedures.     

A Multirate Switching Network for Broadband Channels

A broadband ISDN switching network model is presented, switching the channel types H2, H3, and H4 envisaged by the CCITT. The synchronous time division multiplex technique is applied. The switching network operates at the basic bit rate of the H2-channel; H3and H4-connections are established via multichannel connections of up to four basic channels. H2-connections which are part of one H3- or H4-connection always have to use common interconnection links. This is a favorable solution to keep digit sequence integrity for multichannel connections, but influences blocking characteristics of the switching network. The implementation of an optimal path selection method plays a fundamental role. In such a multichannel switching network, blocking probabilities for H2-, H3-, and H4-connections must be distinguished. They do not only depend on the total offered load, but also on the proportions of H2-, H3-, and H4-connections (traffic mix). The simulation results presented in this paper prove that multirate switching via multichannel connections is feasible for the broadband channel types H2, H3, and H4, and that the proposed switching network has a sufficiently high traffic capacity whatever the traffic mix may be.     

Should Degenerated Intervertebral Discs of Patients with Modic Type 1 Changes Be Treated with Mesenchymal Stem Cells?

Low back pain (LBP) has been among the leading causes of disability for the past 30 years. This highlights the need for improvement in LBP management. Many clinical trials focus on developing treatments against degenerative disc disease (DDD). The multifactorial etiology of DDD and associated risk factors lead to a heterogeneous patient population. It comes as no surprise that the outcomes of clinical trials on intradiscal mesenchymal stem cell (MSC) injections for patients with DDD are inconsistent. Intradiscal MSC injections have demonstrated substantial pain relief and significant disability-related improvements, yet they have failed to regenerate the intervertebral disc (IVD). Increasing evidence suggests that the positive outcomes in clinical trials might be attributed to the immunomodulatory potential of MSCs rather than to their regenerative properties. Therefore, patient stratification for inflammatory DDD phenotypes may (i) better serve the mechanisms of action of MSCs and (ii) increase the treatment effect. Modic type 1 changes—pathologic inflammatory, fibrotic changes in the vertebral bone marrow—are frequently observed adjacent to degenerated IVDs in chronic LBP patients and represent a clinically distinct subpopulation of patients with DDD. This review discusses whether degenerated IVDs of patients with Modic type 1 changes should be treated with an intradiscal MSC injection.     

Elektrische Leitfähigkeit von kugelförmigem Kupferpulver unter Druck

Übersicht Die elektrische Leitfähigkeit von kugelförmigem Kupferpulver verhält sich zwischen 50 bar und 500 bar proportional zum Preßdruck und steigt im Bereicht zwischen 4 m und 25 m ebenfalls annähernd proportional mit dem Korndurchmesser an. Dies steht i m Einklang zu theoretischen Erwartungen. Bei höherem Druck und inbesondere bei groben Kornfraktionen auftretende Abweichungen lassen sich durch die Zerstörung der auf der Oberfläche der Pulverkörner vorhandenen Oxidschicht erklären.

---

On the electric conductivity of compressed spherical copper powder

Contents The electric conductivity of copper powder of spherical particle shape approximately increases proportionally to both the applied pressure in the range between 50 bar and 500 bar and the grain diameter between 4 m and 25 m. This is in agreement with known theory. At higher pressures deviations have been observed, especially at large grain diameters. This may be expalined by the damage of oxide layers on the surface of the powder particles.

     

Electric conductivity of compressed copper powder. Ageing and influence of electric field strength

The conductivity of copper powder can be characterized by the initial conductivity κ₁ at low pressure, the critical pressure p_c, where the conductivity rises steeply, and the final conductivity κ₂ at high pressure. The conductivity has been measured in the pressure range of 1 to 200 MPa, applying low-frequency a.c., during a period of 5 years. Ageing results in a marked increase of p_c and κ₂.In spite of this, the initial conductivity κ₁ depends above all on the electric field strength. It has been measured in the range of 3 to 145 V/cm, followed by a conductivity rise of more than 3 decades. The field influence proceeds in two steps: first a nearly reversible increase of a factor 2; second, after a breakthrough, an irreversible increase, limited only by the temperature limits of the insulating press tool. Local temperatures of more than 250°C have been evaluated.     

Die Druckabhängigkeit der elektrischen Leitfähigkeit von pulverförmigen Oxiden im System Bleidioxid/Mennige

Zusammenfassung Für verschiedene Sauerstoffkonzentrationen von Bleioxidpulver wird die elektrische Leitfähigkeit in Abhängigkeit vom Pressdruck angegeben. Mit abnehmendem Sauerstoffgehalt ist im Bereich zwischen PbO₂ und Pb₃O₄ eine Abnahme der Leitfähigkeit um etwa 16 Zehnerpotenzen zu verzeichnen. Auffallend ist dabei daß der spezifische Widerstand in Abhängigkiet von der Sauerstoffkonzentration eine Stufe aufweist sowie einen Bereich starker Druckabhängigkeit der Leitfähigkeit. Eine Interpretation der Ergebnisse wird im Rahmen bekannter Theorien über die elektrische Leitfähigkeit komprimierter Pulver angegeben. Röntgenstrukturuntersuchungen zeigen die Ausbildung von zwei intermediären Oxiden im untersuchten Bereich:-PbO _x mit einer Zusammensetzung von etwax=l.6 und-PbO _x mitx=l.46.

---

The electric conductivity as a function of the applied pressure has been measured for lead oxide powders of various oxygen contents. In the range between PbO₂ and Pb₃O₄ the conductivity decreases by about 16 dec with decreasing oxygen content and shows a plateau between PbO_1.7 and PbO_1.6. An interpretation of the results is given using known theories of the pressure dependence of powder conductivity. X-ray diffraction analysis shows two intermediate oxides in the observed range:-PbO _x at a composition of aboutx=1.6 and-PbO _x atx=1.46.