The neural basis of centre-surround interactions in visual motion processing

Perception of a moving visual stimulus can be suppressed or enhanced by surrounding context in adjacent parts of the visual field. We studied the neural processes underlying such contextual modulation with fMRI. We selected motion selective regions of interest (ROI) in the occipital and parietal lobes with sufficiently well defined topography to preclude direct activation by the surround. BOLD signal in the ROIs was suppressed when surround motion direction matched central stimulus direction, and increased when it was opposite. With the exception of hMT+/V5, inserting a gap between the stimulus and the surround abolished surround modulation. This dissociation between hMT+/V5 and other motion selective regions prompted us to ask whether motion perception is closely linked to processing in hMT+/V5, or reflects the net activity across all motion selective cortex. The motion aftereffect (MAE) provided a measure of motion perception, and the same stimulus configurations that were used in the fMRI experiments served as adapters. Using a linear model, we found that the MAE was predicted more accurately by the BOLD signal in hMT+/V5 than it was by the BOLD signal in other motion selective regions. However, a substantial improvement in prediction accuracy could be achieved by using the net activity across all motion selective cortex as a predictor, suggesting the overall conclusion that visual motion perception depends upon the integration of activity across different areas of visual cortex

An evaluation of human factors research for ultrasonic inservice inspection

This work was undertaken to determine if human factors research has yielded information applicable to upgrading requirements in ASME Boiler and Pressure Vessel Code Section XI, improving methods and techniques in Section V, and/or suggesting relevant research. A preference was established for information and recommendations which have become accepted and standard practice. Manual Ultrasonic Testing/Inservice Inspection (UT/ISI) is a complex task subject to influence by dozens of variables. This review frequently revealed equivocal findings regarding effects of environmental variables as well as repeated indications that inspection performance may be more, and more reliably, influenced by the workers` social environment, including managerial practices, than by other situational variables. Also of significance are each inspector`s relevant knowledge, skills, and abilities, and determination of these is seen as a necessary first step in upgrading requirements, methods, and techniques as well as in focusing research in support of such programs, While understanding the effects and mediating mechanisms of the variables impacting inspection performance is a worthwhile pursuit for researchers, initial improvements in industrial UTASI performance may be achieved by implementing practices already known to mitigate the effects of potentially adverse conditions. 52 refs., 2 tabs

Patella malalignment, pain and patellofemoral progression: the Health ABC Study

SummaryObjectivePatellofemoral (PF) joint osteoarthritis (OA) is strongly correlated with lower extremity disability and knee pain. Risk factors for pain and structural progression in PF OA are poorly understood. Our objective was to determine the association between patella malalignment and its relation to pain severity, and PF OA disease progression.MethodsWe conducted an analysis of data from the Health ABC knee OA study. Health ABC is a community based, multi-center cohort study of 3075 Caucasian and Black men and women aged 70–79 at enrollment. Weight bearing skyline knee X-rays were obtained in a subset (595) of subjects, with and without knee pain, at year 2 and year 5 (mean follow-up 36 months). Films were read paired, and PF osteophytes (OST) and joint space narrowing (JSN) were scored on a 0–3 scale using the Osteoarthritis Research Society International atlas. We defined progression of PF OA as any increase in JSN score. Three measures of patella malalignment were made: sulcus angle; patella tilt angle; and patella subluxation medially or laterally (bisect offset). Knee symptoms were assessed using a knee specific Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) knee pain subscale. We assessed the relationship between baseline patella malalignment and pain severity (linear regression for WOMAC) and compartment specific PF OA progression (logistic regression for dichotomous outcomes). We classified continuous measures of patella alignment into quartile groups. We performed multivariable adjusted logistic regression models, including age, gender and body mass index (BMI) to assess the relation of baseline patella alignment to the occurrence of PF JSN progression using generalized estimating equations (GEE).ResultsThe subjects had a mean age 73.6 (SD 2.9), BMI 28.8 (SD 4.9), 40.3% male, and 46% were Black. Medial displacement of the patella predisposed to medial JSN progression; odds for each quartile 1, 1.2, 1.2, 2.2 (P for trend=0.03), whilst protecting from lateral JSN progression; odds for each quartile 1, 0.7, 0.6, 0.4 (P for trend=0.0004). Increasing patella tilt protected from medial JSN progression; odds for each quartile 1, 0.8, 0.5, 0.2 (P<0.0001) and trended to increasing pain severity (P=0.09).ConclusionPatella malalignment is associated with PF disease progression. Medial displacement and tilt of the patella predisposes to medial JSN progression, whilst lateral displacement is predictive of lateral JSN progression. The influence of patella malalignment has important implications since it is potentially modifiable through footwear, taping and/or knee bracing

On the magnetic stability at the surface in strongly correlated electron systems

The stability of ferromagnetism at the surface at finite temperatures is investigated within the strongly correlated Hubbard model on a semi-infinite lattice. Due to the reduced surface coordination number the effective Coulomb correlation is enhanced at the surface compared to the bulk. Therefore, within the well-known Stoner-picture of band ferromagnetism one would expect the magnetic stability at the surface to be enhanced as well. However, by taking electron correlations into account well beyond the Hartree-Fock (Stoner) level we find the opposite behavior: As a function of temperature the magnetization of the surface layer decreases faster than in the bulk. By varying the hopping integral within the surface layer this behavior becomes even more pronounced. A reduced hopping integral at the surface tends to destabilize surface ferromagnetism whereas the magnetic stability gets enhanced by an increased hopping integral. This behavior represents a pure correlation effect and can be understood in terms of general arguments which are based on exact results in the limit of strong Coulomb interaction.Comment: 6 pages, RevTeX, 4 eps figures, accepted (Phys. Rev. B), for related work and info see http://orion.physik.hu-berlin.d

Generation of entangled coherent states via cross phase modulation in a double electromagnetically induced transparency regime

The generation of an entangled coherent state is one of the most important ingredients of quantum information processing using coherent states. Recently, numerous schemes to achieve this task have been proposed. In order to generate travelling-wave entangled coherent states, cross phase modulation, optimized by optical Kerr effect enhancement in a dense medium in an electromagnetically induced transparency (EIT) regime, seems to be very promising. In this scenario, we propose a fully quantized model of a double-EIT scheme recently proposed [D. Petrosyan and G. Kurizki, {\sl Phys. Rev. A} {\bf 65}, 33833 (2002)]: the quantization step is performed adopting a fully Hamiltonian approach. This allows us to write effective equations of motion for two interacting quantum fields of light that show how the dynamics of one field depends on the photon-number operator of the other. The preparation of a Schr\"odinger cat state, which is a superposition of two distinct coherent states, is briefly exposed. This is based on non-linear interaction via double-EIT of two light fields (initially prepared in coherent states) and on a detection step performed using a $50:50$ beam splitter and two photodetectors. In order to show the entanglement of a generated entangled coherent state, we suggest to measure the joint quadrature variance of the field. We show that the entangled coherent states satisfy the sufficient condition for entanglement based on quadrature variance measurement. We also show how robust our scheme is against a low detection efficiency of homodyne detectors.Comment: 15 pages, 9 figures; extensively revised version; added Section

Pressure Studies on a High-TcT_c Superconductor Pseudogap and Critical Temperatures

We report simultaneous hydrostatic pressure studies on the critical temperature $T_c$ and on the pseudogap temperature $T^*$ performed through resistivity measurements on an optimally doped high-$T_c$ oxide $Hg_{0.82}Re_{0.18}Ba_2Ca_2Cu_3O_{8+\delta}$. The resistivity is measured as function of the temperature for several different applied pressure below 1GPa. We find that both $T_c$ and $T^*$ increases linearly with the pressure. This result demonstrate that the well known intrinsic pressure effect on $T_c$ is also present at $T^*$ and both temperatures are originated by the same superconducting mechanism.Comment: 4 pages and 2 figures in eps, final versio

Evaluating Microcounseling Training

An evaluation research design was developed as an attempt to provide a more satisfactory approach to microcounseling training program evaluation. Trainee performance was measured three times during a counseling practicum, with microcounseling training occurring between the second and third observations. Trainee performance was compared to a predetermined standard for counselor behavior. Results were analyzed for both the differences between observations, and the degree of similarity to the model. Counseling behavior of trainees after microcounseling training was significantly different from their behavior prior to the training. After training they were more like the standard. The trainees performed less like the standard after some counseling experience, but before receiving microcounseling training.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/66901/2/10.1177_0193841X8300700206.pd

The Casimir force and the quantum theory of lossy optical cavities

We present a new derivation of the Casimir force between two parallel plane mirrors at zero temperature. The two mirrors and the cavity they enclose are treated as quantum optical networks. They are in general lossy and characterized by frequency dependent reflection amplitudes. The additional fluctuations accompanying losses are deduced from expressions of the optical theorem. A general proof is given for the theorem relating the spectral density inside the cavity to the reflection amplitudes seen by the inner fields. This density determines the vacuum radiation pressure and, therefore, the Casimir force. The force is obtained as an integral over the real frequencies, including the contribution of evanescent waves besides that of ordinary waves, and, then, as an integral over imaginary frequencies. The demonstration relies only on general properties obeyed by real mirrors which also enforce general constraints for the variation of the Casimir force.Comment: 18 pages, 6 figures, minor amendment