Luminance-dependent hue shift in protanopes

For normal trichromats, the hue of a light can change as its luminance varies. This Bezold-Brücke (B-B) hue shift is commonly attributed to nonlinearity in the blue–yellow opponent system. In the present study, we questioned whether protanopes experience analogous changes. Two protanopes (Ps) viewed spectral lights at six luminance levels across three log steps. Two normal trichromats (NTs) were tested for comparison. A variant of the color-naming method was used, with an additional “white” term. To overcome the difficulty of Ps’ idiosyncratic color naming, we converted color-naming functions into individual color spaces, by way of interstimulus similarities and multidimensional scaling (MDS). The color spaces describe each stimulus in terms of spatial coordinates, so that hue shifts are measured geometrically, as displacements along specific dimensions. For the NTs, a B-B shift derived through MDS agreed well with values obtained directly by matching color-naming functions. A change in color appearance was also observed for the Ps, distinct from that in perceived brightness. This change was about twice as large as the B-B shift for NTs and combined what the latter would distinguish as hue and saturation shifts. The protanopic analogue of the B-B shift indicates that the blue–yellow nonlinearity persists in the absence of a red–green signal. In addition, at mesopic levels (# 38 td), the Ps’ MDS solution was two dimensional at longer wavelengths, suggesting rod input. Conversely, at higher luminance levels (76 td–760 td) the MDS solution was essentially one dimensional, placing a lower limit on S-cone input at longer wavelengths

A whiter shade of pale, a blacker shade of dark: Parameters of spatially induced blackness

The surface-mode property of “blackness” is induced by simultaneous contrast with an adjacent, more luminant surround. As numerous studies have shown, the degree of blackness induced within an achromatic test field is a function of the relative luminance of the adjacent chromatic inducing field, but not of its hue. But in the converse case of chromatic test fields, susceptibility to blackening has been reported to vary with wavelength. The present study investigates this possibility, that some wavelengths are more susceptible. We also questioned whether “white” and “black” sensory components function as opposites in blackness appearance. We recorded the appearance of a central monochromatic test field of constant luminance (10 cd/m2), with wavelength ranging across the visible spectrum, while a broadband white annulus was set to six luminance levels ranging across three log steps. Three color-normal observers followed a color-naming technique. All six opponent-hue names and their combinations were response options; blackness and whiteness in the test field could therefore be reported independently. Of primary interest were the achromatic responses. When represented within a multidimensional space, these revealed the “white-to-black” dimension but in addition a quality ~dimension! of “desaturation.” Compared against chromatic properties of the test field, the results provide evidence that blackness is a function of inducing field brightness (not luminance). This result is in accord with observations made by Shinomori et al. (1997) using a different procedure. We conclude that blackness induction occurs at a stage of visual processing subsequent to the origin of the brightness signal from a combination of opponent-process channels

Multidimensional Coherent Spectroscopy of a Semiconductor Microcavity

Rephasing and non-rephasing two-dimensional coherent spectra map the anti-crossing associated with normal-mode splitting in a semiconductor microcavity. For a 12-meV detuning range near zero detuning, it is observed that there are two diagonal features related to the intra-action of exciton-polariton branches and two off-diagonal features related to coherent interaction between the polaritons. At negative detuning, the lineshape properties of the diagonal intra-action features are distinguishable and can be associated with cavity-like and exciton-like modes. A biexcitonic companion feature is observed, shifted from the exciton feature by the biexciton binding energy. Closer to zero detuning, all features are enhanced and the diagonal intra-action features become nearly equal in amplitude and linewidth. At positive detuning the exciton- and cavity-like characteristics return to the diagonal intra-action features. Off-diagonal interaction features exhibit asymmetry in their amplitudes throughout the detuning range. The amplitudes are strongly modulated (and invert) at small positive detuning, as the lower polariton branch crosses the bound biexciton energy determined from negative detuning spectra.Comment: 13 pages, 4 figure

Facial-Expression Affective Attributes and their Configural Correlates: Components and Categories

The present study investigates the perception of facial expressions of emotion, and explores the relation between the configural properties of expressions and their subjective attribution. Stimuli were a male and a female series of morphed facial expressions, interpolated between prototypes of seven emotions (happiness, sadness, fear, anger, surprise and disgust, and neutral) from Ekman and Friesen (1976). Topographical properties of the stimuli were quantified using the Facial Expression Measurement (FACEM) scheme. Perceived dissimilarities between the emotional expressions were elicited using a sorting procedure and processed with multidimensional scaling. Four dimensions were retained in the reconstructed facial-expression space, with positive and negative expressions opposed along D1, while the other three dimensions were interpreted as affective attributes distinguishing clusters of expressions categorized as “Surprise-Fear,” “Anger,” and “Disgust.” Significant relationships were found between these affective attributes and objective facial measures of the stimuli. The findings support a componential explanatory scheme for expression processing, wherein each component of a facial stimulus conveys an affective value separable from its context, rather than a categorical-gestalt scheme. The findings further suggest that configural information is closely involved in the decoding of affective attributes of facial expressions. Configural measures are also suggested as a common ground for dimensional as well as categorical perception of emotional faces.Este estudio investiga la percepción de las expresiones faciales de la emoción y explora la relación entre las propiedades configurales de las expresiones y su atribución subjetiva. Los estímulos eran una serie de expresiones faciales transformadas por ordenador, interpuestas entre los prototipos de siete emociones (felicidad, tristeza, miedo, ira, sorpresa, asco y neutral) tomados de Ekman y Friesen (1976). Las propiedades topográficas de los estímulos se cuantificaron mediante el esquema Facial Expression Measurement (FACEM). Las disimilaridades percibidas entre las expresiones emocionales se elicitaron mediante un procedimiento de clasificación y se procesaron con escalonamiento multidimensional. Se retuvieron cuatro dimensiones en el espacio facial-expresión reconstruido, con expresiones positivas y negativas contrapuestas a lo largo de D1, y las restantes tres dimensiones se interpretaron como atributos afectivos, distinguiendo clusters de expresiones clasificadas como “Sorpresa/Miedo”, “Ira”, y “Asco”. Se hallaron relaciones significativas entre estos atributos afectivos y las medidas faciales objetivas de los estímulos. Los resultados apoyan un esquema explicativo componencial para el procesamiento de las expresiones, en el que cada componente de un estímulo facial conlleva un valor afectivo separable de su contexto, más que un esquema categórico de tipo Gestalt. Además sugieren que la información configural juega un papel importante en la decodificación de los atributos afectivos de las expresiones faciales Además, sugieren que las medidas configurales constituyen en terreno común de la percepción dimensional y categórica de las caras emocionales

Testing Gravity and Predictions Beyond the Standard Model at Short Distances: The Casimir Effect

The Standard Model of elementary particles and their interactions does not include the gravitational interaction and faces problems in understanding of the dark matter, dark energy, strong CP violation etc. In continuing attempts to solve these problems, many predictions of new light elementary particles and hypothetical interactions beyond the Standard Model have been made. These predictions can be constrained by many means and, specifically, by measuring the Casimir force arising between two closely spaced bodies due to the zero-point and thermal fluctuations of the electromagnetic field. After a brief survey in the theory of the Casimir effect, the strongest constraints on the power-type and Yukawa-type corrections to Newtonian gravity, following from measuring the Casimir force at short distances, are considered. Next,the problems of dark matter, dark energy and their probable constituents are discussed. This is followed by an analysis of constraints on the dark matter particles, and, specifically, on axions and axionlike particles, obtained from the Casimir effect. The question of whether the Casimir effect can be used for constraining the spin-dependent interactions is also considered. Then the constraints on the dark energy particles, like chameleons and symmetrons, are examined. In all cases the subject of our treatment is not only measurements of the Casimir force but some other relevant table-top experiments as well. In conclusion, the prospects of the Casimir effect for constraining theoretical predictions beyond the Standard Model at short distances are summarized.Comment: 40 pages, 5 figure

Casimir Effect Invalidates the Drude Model for Transverse Electric Evanescent Waves

We consider the Casimir pressure between two metallic plates and calculate the four contributions to it determined by the propagating and evanescent waves and by the transverse magnetic and transverse electric polarizations of the electromagnetic field. The range of interplate separations is considered where nearly the whole pressure has its origin in the electromagnetic response of conduction electrons. In the Casimir physics, this response is described either by the dissipative Drude model resulting in contradictions with the measurement data or by the experimentally consistent but dissipationless plasma model. It is shown that the total transverse magnetic contribution to the Casimir pressure due to both the propagating and evanescent waves and the transverse electric contribution due to only the propagating waves, computed by means of the Drude model, correlate well with the corresponding results obtained using the plasma model. The conclusion is made that a disagreement between the theoretical predictions obtained using the Drude model and precision measurements of the Casimir force is not caused by the account of dissipation in itself, but arises from an incorrect description of the response of metals to the low-frequency transverse electric evanescent waves by this model. It is demonstrated that the Drude model has no supporting experimental evidence in the range of transverse electric evanescent waves, so that the above conclusion is consistent with all available information. The alternative test of the Drude model for the transverse electric evanescent waves suggested in the framework of classical electrodynamics is discussed.Comment: 15 pages, 5 figure

Large-Separation Behavior of the Casimir-Polder Force from Real Graphene Sheet Deposited on a Dielectric Substrate

The Casimir-Polder force between atoms or nanoparticles and graphene-coated dielectric substrates is investigated in the region of large separations. Graphene coating with any value of the energy gap and chemical potential is described in the framework of the Dirac model using the formalism of the polarization tensor. It is shown that the Casimir-Polder force from a graphene-coated substrate reaches the limit of large separations at approximately 5.6 $\mu$m distance between an atom or a nanoparticle and graphene coating independently of the values of the energy gap and chemical potential. According to our results, however, the classical limit, where the Casimir-Polder force no longer depends on the Planck constant and the speed of light, may be attained at much larger separations depending on the values of the energy gap and chemical potential. In addition, we have found a simple analytic expression for the Casimir-Polder force from a graphene-coated substrate at large separations and determined the region of its applicability. It is demonstrated that the asymptotic results for the large-separation Casimir-Polder force from a graphene-coated substrate are in better agreement with the results of numerical computations for the graphene sheets with larger chemical potential and smaller energy gap. Possible applications of the obtained results in nanotechnology and bioelectronics are discussed.Comment: 15 pages, 6 figure

Histological and immunohistochemical evaluation of mandibular bone tissue regeneration

The purpose of the study was to perform an immunohistochemical and histological evaluation of samples taken from different bone regeneration procedures in atrophic human mandible. 30 patients (15 men and 15 women, age range of 35-60 years), non-smokers, with good general and oral health were recruited in this study and divided into three groups. The first group included patients who were treated with blood Concentration Growth Factors (bCGF), the second group included patients who were treated with a mixture of bCGF and autologous bone, while the third group of patients was treated with bCGF and tricalcium phosphate/hydroxyapatite (TCP-HA). Six months after the regenerative procedures, all patients undergone implant surgery, and a bone biopsy was carried out in the site of implant insertion. Each sample was histologically and immunohistochemically examined. Histological evaluation showed a complete bone formation for group II, partial ossification for group I, and moderate ossification for group III. Immunohistochemical analysis demonstrated a statistically significant difference between the three groups, and the best clinical result was obtained with a mixture of bCGF and autologous bone