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Dynamical black holes in the non-perturbative regime are not mathematically well understood. Studying approximate symmetries of spacetimes describing dynamical black holes gives an insight into their structure. Utilising the property that approximate symmetries coincide with actual symmetries when they are present allows one to construct geometric invariants characterising the symmetry. In this paper, we extend Dain's construction of geometric invariants characterising stationarity to the case of initial data sets for the Einstein equations corresponding to black hole spacetimes. We prove the existence and uniqueness of solutions to a boundary value problem showing that one can always find approximate Killing vectors in black hole spacetimes and these coincide with actual Killing vectors when they are present. In the time-symmetric setting we make use of a 2+1 decomposition to construct a geometric invariant on a MOTS that vanishes if and only if the Killing initial data equations are locally satisfied., 33 pages more...

This paper discusses the importance of construction to the three elements of sustainable development, namely economic growth, social progress and effective protection of the environment. The paper goes on to identify the issues facing construction in meeting the sustainable development agenda; these include efficient use of natural resources, reducing energy consumption, reducing emissions, minimizing waste, more efficient land use, reducing the impact on construction sites and creating better employment conditions. The ways in which steel construction is addressing these issues are discussed. In the context of new buildings, steel’s impact on the construction process—namely speed, prefabrication, safety, waste minimization and factory and site conditions are described. Ways in which construction form can contribute to reducing the energy consumption in buildings, particularly during the “in-use” part of the building’s lifecycle, are outlined. The role of steel in extending the life of existing building stock is examined and design features for enabling re-use of steel components are highlighted. The paper concludes with remarks on the extent to which constructional steel is recovered and recycled at the end of life of buildings. more...

The adaptor cards and driver software for workstations and local asynchronous transfer mode (ATM) switches and switch control software used in an ATM local area network (LAN) system are discussed. It is shown that the ATM hardware and software components together provide services that are essential for ATM to be considered a realistic alternative to current shared-media LANs. These services include: completely transparent support for the TCP/IP protocol suite, an application programming interface for full access to the underlying ATM capabilities, support for AAL5, AAL3/4, and the null AAL, both connection-oriented and connectionless service, dynamic connection establishment or switched virtual circuits, resource reservation of guaranteed bandwidth and quality of service, full-bandwidth multicast and broadcast, virtual path and channel routing among multiple switches, automatic configuration and failure recovery, dynamic address assignment and internetwork address resolution, and network management via the simple network management protocol (SNMP). > more...

ATM (asynchronous transfer mode) is an international telecommunications standard designed for broadband integrated services; it is also well-suited for use within local-area networks. ATM LANs can provide the networking support needed for multimedia communication at rates of 100 Mbits/sec and higher. The authors first analyze the protocol processing required to handle ATM communication. Based on this analysis, they then discuss the architectural issues in the design of host interfaces for ATM local-area networks. In particular, they conclude that a simple host interface, which leaves most of the ATM protocol processing to be done by the host computer, supports good performance for data communication (around 100 Mbits/sec). However, to support real-time video and audio communication, the ATM interface should include an embedded processor. > more...

The results of 250 cadaver kidney transplants performed at this hospital between May 1968 and December 1974 were analysed. A functioning transplant was defined strictly as one that maintained the recipient in good health with a serum creatinine below 442 mumol/1 (5 mg/100 ml) without any need for dialysis. The proportions of kidneys functioning after one, two, and three years were 40-4%, 33-9%, and 31-1% respectively, the corresponding survival rates of patients being 62-6%, 57-4%, and 43-8%. The primary failure rate overall was 21-6%, while the failure rates for first, second, and third transplants were 18-1%, 39-9%, and 66-7% respectively. Half of the primary failures were attributed to the use of cadaver kidneys with abnormal vasculature or long ischaemic times or originating from non-ventilated donors. Of the initially successful transplants 49% were subsequently lost due to rejection (53%) or death of the patient with a functioning transplant (46%), and of the secondary losses 58% occurred within three months of transplantation. HLA matching of donor and recipient for two or more antigens was associated with a significant increase in transplant survival--46% at three years as opposed to 9-5% at three years for kidneys with poorer matches. more...

A retrospective study of 250 cadaver kidney transplants was carried out to determine the effects of the agonal period, the warm and cold ischaemic times, and the use of kidneys with vascular anomalies on the primary success and failure and the subsequent level of function of the transplants. Kidneys with vascular anomalies or from non-ventilated donors had a primary failure rate of over 30%, whereas those with normal vasculature or from ventilated donors had a rate of 17%. An initial warm ischaemic time of more than 60 minutes was associated with a primary failure rate of 57% and a cold ischaemic time of over 550 minutes with a primary failure rate of 47%. The interrelationship between the warm and cold ischaemic times in the primary success or failure of the transplants was examined and criteria defined for selecting potentially viable cadaver kidneys for transplantation, as follows: (1) The donor should be (a) ventilated, (b) aged 6-50 years, and (c) have normal ante-mortem renal function and have secreted more than 1-5 1 of urine in the 24 hours before death (or an equivalent volume if the urinary output was recorded for less than 24 hours before death); (2) the kidney should have normal renal vasculature enabling single arterial and venous anastomoses to be performed; (3) kidneys with I.W.I.T.s of longer than 60 minutes should not be used; (4) for kidneys with I.W.I.T.s of less than 20 minutes the C.I.T. is not critical but should not exceed 12 hours; (5) for kidneys with I.W.I.T.s of 20-60 minutes the C.I.T. should not exceed 450 minutes. more...

In a review of 250 consecutive human cadaveric kidney transplants the primary failure rate of donor kidneys with an anatomically abnormal blood supply was 36.7% as compared with 16.2% for kidneys with a single artery and vein (P less than 0.001). The incidence of primary failure due to renal vascular thrombosis in the abnormal group was 24.2%, compared with 4.1% in the normal group (P greater than 0.001). A significantly greater incidence of anastomotic haemorrhage and urinary leak was also associated with an abnormal blood supply in the donor kidney. more...

The production and quality control of ALG are outlined. The advantages and disadvantages of the various routes of administration of ALG are discussed. We tend to use a short duration high dose course of ALG in renal transplantation, myasthenia gravis and polyarteritis nodosa. more...

In controlled randomized study of antilymphocyte globulin (ALG) in 100 cadaveric renal transplants, 15 patients receiving a second transplant were excluded. Ofthe first transplants, 42 were in the control and 43 in the ALG group. The two groups were similar. The ALG used was either prodduced in our laboratories or obtained from a commerical source. It was observed that ALG produced a significant lymphopenia, that the oliguric phase of the ALG group was half that of the controls, and that the ALG group although less likely to suffer rejection episodes responded significantly better when treated than did those in the control group. more...