Manager Associate [IKBS]

The knowledge-based Manager Associate, which assists managers in planning, organizing, staffing, scheduling, measuring, visualizing, and controlling software development processes, is described. The Manager Associate operates in a distributed Unix environment in which the manager has access to the software developer workstations through a computer network. The Manager Associate helps managers anticipate problems, which allow early corrective action. As a result, software projects can be developed on time, within budget, and to customer satisfaction     

InP/InGaAsP double-heterostructure optoelectronic switch

The double-heterostructure optoelectronic switch (DOES), fabricated in the InP/InGaAsP material system, is demonstrated. The functional characteristics and operational parameters exhibit a lower switching voltage (≈1.8 V) and a higher on-state holding current (≈20 mA) than found in either the Si/SiGe- or GaAs/AlGaAs-based DOES of comparable structures and doping levels. In the on-state, optical emission is observed in a manner analogous to a light emitting diode. However, enhanced optical emission is observed when the device is biased in the regime of negative differential resistance     

Extreme field-induced cyclotron mass variations in coupled double quantum wells

We observe deviations in the cyclotron effective mass m_c near the partial energy gap formed in strongly coupled GaAs double quantum wells (QWs) subject to in-plane magnetic fields B. In k-space, B shifts the two QW dispersion curves relative to one another, resulting in an anticrossing and opening the energy gap. This gives rise to large B-tunable distortions in the Fermi surface and density of states. This system is thus unique in that the Fermi surface and energy position of the gap can be controlled by sweeping B. Recently, Lyo has predicted that m_c undergoes large variations as the partial energy gap is moved through the Fermi level by B. By tilting our sample by a small angle θ, we introduce a small perpendicular magnetic field B, in addition to B, and analyze the temperature dependence of the resulting Shubnikov-de Haas oscillations to obtain m_c(B). Due to the strongly distorted dispersion near the gap, m_c is suppressed by more than a factor of 3 near the upper gap edge, and enhanced by 50% near the lower gap edge, in excellent agreement with the theory of Lyo. We also observe the quantum Hall effect in a double QW at a high, constant B.     

The functional anatomy of imagining and perceiving colour

OBJECTIVE: To determine whether the progression of urinary albumin excretion rate (AER) is higher during puberty than before or after this period. RESEARCH DESIGN AND METHODS: A prospective study was conducted in which normoalbuminuric prepubertal (n = 20), pubertal (n = 28), and postpubertal (n = 26) IDDM groups matched for diabetes duration and long-term metabolic control were followed for 3 years. At 6-month intervals, 24-h urine collection was used to determine AER. RESULTS: AER increased significantly over a period of 3 years in the pubertal (P = 0.001) and postpubertal (P = 0.003) subjects but not in prepubertal subjects. The annual progression of AER was significantly higher in the pubertal group than in the prepubertal (P = 0.001) or postpubertal (P = 0.001) groups. Six pubertal, two postpubertal, and none of the prepubertal subjects developed microalbuminuria (AER > or = 20 micrograms/min on two consecutive occasions) over a 3-year period (P = 0.047). Multiple logistic regression analysis showed that the risk of development of microalbuminuria was increased in pubertal subjects compared with the prepubertal and postpubertal subjects (adjusted relative risk [95% CI]: 4.3 [1.5-9.3], P = 0.012, and 2.1 [1.1-5.0], P = 0.023, respectively). CONCLUSIONS: Puberty represents an independent risk of the development of microalbuminuria in diabetes. This findings suggests that the endocrine changes of puberty lead to an accelerated process of early kidney damage in diabetes. In pediatric diabetes care, screening for microalbuminuria is needed soon after the onset of puberty.     

NT-3, but not BDNF, prevents atrophy and death of axotomized spinal cord projection neurons

Following spinal cord injury, projection neurons are frequently axotomized and many of the cells subsequently die. One goal in spinal injury research is to preserve damaged neurons so that ultimately they are accessible to regeneration-promoting strategies. Here we ask if neurotrophin treatment can prevent atrophy and death of axotomized sensory projection neurons. In adult rats, a hemisection was made in the thoracic spinal cord and axotomized neurons were retrogradely labelled with Fluoro-Gold. Four distinct populations of cells were identified in the lumbar spinal cord, and both numbers and sizes of labelled cells were assessed at different time points postlesion. A progressive and significant degeneration was observed over time with severe atrophy apparent in all cell populations and significant cell loss evident by 4 weeks postlesion. This time point was used to assess neurotrophin effects. Hemisected rats were treated with either neurotrophin 3 (NT-3) or brain-derived neurotrophic factor (BDNF, 12 microg/day for each), or a vehicle solution, delivered continuously to the lesion site via an osmotic minipump. Treatment with NT-3, but not BDNF, completely reversed cell atrophy in three of the four cell populations and also induced a significant increase in the number of surviving cells. In situ hybridization experiments showed trkB and trkC mRNA to be expressed in the majority of ascending spinal projection neurons, suggesting that these cells should be responsive to both BDNF and NT-3. However, only NT-3 treatment was neuroprotective, indicating that BDNF may not have reached the cell bodies of injured neurons. These results demonstrate that NT-3 may be of benefit in preventing the secondary cell loss that occurs following spinal injury.     

Well number, length, and temperature dependence of efficiency andloss in InGaAsP-InP compressively strained MQW ridge waveguide lasers at1.3 μm

Experimental measurements of external differential efficiency on 0.7% compressively strained multiquantum-well (MQW) ridge waveguide lasers operating at 1.3 μm are presented. The lasers have the number of quantum wells (QW's) varying from 5 to 14 and cavity lengths ranging from 250 to 1000 μm and were measured over a temperature range of -50°C to 90°C. A phenomenological model is introduced which shows that over a range of design and operating conditions, the behavior of the external differential quantum efficiency can be entirely explained by intervalence band absorption (IVBA) It is also shown that outside this range IVBA alone is not sufficient to describe the behavior, indicating that current leakage becomes a significant factor. Ramifications of the IVBA contribution to the external differential quantum efficiency are investigated     

Trends disrupted—patent information in an era of change

Patent analysts predict trends in research and the business environment by studying the numbers and classifications of patents issued to companies around the world. Those attempts are often affected by the changes taking place in international treaties, governments, patent laws, patent classification systems, and corporate mergers and acquisitions. This paper describes some of the changes in the patent information environment that have disrupted the trends predicted by patent analyses in the past.     

The effect of varying barrier height on the operationalcharacteristics of 1.3-μm strained-layer MQW lasers

This paper presents an empirical study of the effects that barrier layer composition has on the operational characteristics of 1.3-μm-wavelength InGaAsP-InP multiquantum-well (MQW) strained-layer ridge-waveguide lasers. A systematic empirical investigation of how this design choice affects practical device operation was undertaken by examining threshold current, efficiency, and modal gain as a function of temperature in five different laser structures. The results of these studies indicate that small barrier heights improve device performance, despite the loss of electronic confinement in the shallow conduction band quantum wells. Indeed, it appears that carrier uniformity in the MQW structure may be improved by carrier redistribution due to thermal or tunneling effects, which in turn enhances the operation of the low barrier height structures     

Results concerning the bandwidth of subliminal channels

In conjunction with a six-month research program on computer security, cryptology and coding theory hosted by the Isaac Newton Institute of Mathematical Sciences, University of Cambridge, Cambridge, U.K., a Workshop on information hiding was held from May 30 through June 1, 1996. This workshop was devoted to all aspects of information hiding - other than the usual cryptographic concealment of content, including steganography, subliminal channels, fingerprinting, covert channels, etc. Two surprising results pertaining to subliminal channels were presented or grew out of presentations made at this workshop. One is of interest to the secure communications protocol designer concerned with denying the use of subliminal channels, while the other is important to the designer, or user, of subliminal channels. The first raises the question of whether the notion of a “subliminal-free” communication channel is an oxymoron, i.e., is it possible to force the bandwidth of the subliminal channel to be truly zero? The second forces a more precise formulation of a conjecture the author had made that the bandwidth of a subliminal channel is logarithmically limited if the transmitter is unwilling to trust the subliminal receiver unconditionally. Motivated by these results, this paper reexamines the fundamental questions of the bandwidth available for subliminal communication as a function of the trust the transmitter has in the subliminal receiver and of a logically sound interpretation of the term “subliminal-free”