1,387 research outputs found
Geologic and mineral and water resources investigations in western Colorado, using Skylab EREP data
The author has identified the following significant results. Skylab photographs are superior to ERTS images for photogeologic interpretation, primarily because of improved resolution. Lithologic contacts can be detected consistently better on Skylab S190A photos than on ERTS images. Color photos are best; red and green band photos are somewhat better than color-infrared photos; infrared band photos are worst. All major geologic structures can be recognized on Skylab imagery. Large folds, even those with very gentle flexures, can be mapped accurately and with confidence. Bedding attitudes of only a few degrees are recognized; vertical exaggeration factor is about 2.5X. Mineral deposits in central Colorado may be indicated on Skylab photos by lineaments and color anomalies, but positive identification of these features is not possible. S190A stereo color photography is adequate for defining drainage divides that in turn define the boundaries and distribution of ground water recharge and discharge areas within a basin
Smoothing effect and delocalization of interacting Bose-Einstein condensates in random potentials
We theoretically investigate the physics of interacting Bose-Einstein
condensates at equilibrium in a weak (possibly random) potential. We develop a
perturbation approach to derive the condensate wavefunction for an amplitude of
the potential smaller than the chemical potential of the condensate and for an
arbitrary spatial variation scale of the potential. Applying this theory to
disordered potentials, we find in particular that, if the healing length is
smaller than the correlation length of the disorder, the condensate assumes a
delocalized Thomas-Fermi profile. In the opposite situation where the
correlation length is smaller than the healing length, we show that the random
potential can be significantly smoothed and, in the meanfield regime, the
condensate wavefunction can remain delocalized, even for very small correlation
lengths of the disorder.Comment: The word "screening" has been changed to "smoothing" to avoid
confusions with other effects discussed in the literature. This does not
affect the content of paper, nor the results, nor the physical discussio
Social relationships and depression during the COVID-19 lockdown: longitudinal analysis of the COVID-19 social study
Background. The coronavirus disease 2019 (COVID-19) pandemic led to measures that
reduced social contact and support. We explored whether UK residents with more frequent
or supportive social contact had fewer depressive symptoms during March−August 2020,
and potential factors moderating the relationship.
Methods. A convenience sample of UK dwelling participants aged ⩾18 in the internet-based
longitudinal COVID-19 Social Study completed up to 22 weekly questionnaires about face-toface and phone/video social contact frequency, perceived social support, and depressive symptoms using the PHQ-9. Mixed linear models examined associations between social contact
and support, and depressive symptoms. We examined for interaction by empathic concern,
perspective taking and pre-COVID social contact frequency.
Results. In 71 117 people with mean age 49 years (standard deviation 15), those with high
perceived social support scored 1.836 (1.801–1.871) points lower on PHQ-9 than those
with low support. Daily face-to-face or phone/video contact was associated with lower depressive symptoms (0.258 (95% confidence interval 0.225–0.290) and 0.117 (0.080–0.154),
respectively) compared to no contact. The negative association between social relationships
and depressive symptoms was stronger for those with high empathic concern, perspective
taking and usual sociability.
Conclusions. We found during lockdown that those with higher quality or more face-to-face
or phone/video contact had fewer depressive symptoms. Contact quality was more strongly
associated than quantity. People who were usually more sociable or had higher empathy
had more depressive symptoms during enforced reduced contact. The results have implications for COVID-19 and potential future pandemic management, and for understanding
the relationship between social factors and mental health
Influence of Strong Acid Hydrolysis Processing on the Thermal Stability and Crystallinity of Cellulose Isolated from Wheat Straw
Cellulose extractions from wheat straw via hydrochloric, nitric, and sulfuric acid hydrolysis methods were carried out. X-ray diffraction spectral analyses reveal that depending on the acid conditions used the structure of the cellulose exhibited a mixture of polymorphs (i.e., CI and CIII cellulose phases). In addition, the percent crystallinity, diameter, and length of the cellulose fibers varied tremendously as determined by X-ray diffraction and scanning electron microscopy. Thermal gravimetric analysis measurements revealed that the thermal stability of the extracted cellulose varied as a function of the acid strength and conditions used. Scanning electron microscopy analysis revealed that the aggregation of cellulose fibers during the drying process is strongly dependent upon the drying process and strength of the acids used
Bosons in Disordered Optical Potentials
In this work we systematically investigate the condensate properties,
superfluid properties and quantum phase transitions in interacting Bose gases
trapped in disordered optical potentials. We numerically solve the Bose-Hubbard
Hamiltonian exactly for different: (a) types of disorder, (b) disorder
strengths, and (c) interatomic interactions. The three types of disorder
studied are: quasiperiodic disorder, uniform random disorder and random
speckle-type disorder. We find that the Bose glass, as identified by Fisher et
al [Phys. Rev. B {\bf 40}, 546 (1989)], contains a normal condensate component
and we show how the three different factors listed above affect it.Comment: 4 pages, 4 figures (low res) v2 Title,Abstract,Introduction: changes;
Figure 3: Add label to axi
Assessing awareness in severe Alzheimer’s disease
There is an urgent need to understand the nature of awareness in people with severe Alzheimer’s disease (AD) to ensure effective person-centered care. Objective biomarkers of awareness validated in other clinical groups (e.g., anesthesia, minimally conscious states) offer an opportunity to investigate awareness in people with severe AD. In this article we demonstrate the feasibility of using Transcranial magnetic stimulation (TMS) combined with EEG, event related potentials (ERPs) and fMRI to assess awareness in severe AD. TMS-EEG was performed in six healthy older controls and three people with severe AD. The perturbational complexity index (PCIST) was calculated as a measure of capacity for conscious awareness. People with severe AD demonstrated a PCIST around or below the threshold for consciousness, suggesting reduced capacity for consciousness. ERPs were recorded during a visual perception paradigm. In response to viewing faces, two patients with severe AD provisionally demonstrated similar visual awareness negativity to healthy controls. Using a validated fMRI movie-viewing task, independent component analysis in two healthy controls and one patient with severe AD revealed activation in auditory, visual and fronto-parietal networks. Activation patterns in fronto-parietal networks did not significantly correlate between the patient and controls, suggesting potential differences in conscious awareness and engagement with the movie. Although methodological issues remain, these results demonstrate the feasibility of using objective measures of awareness in severe AD. We raise a number of challenges and research questions that should be addressed using these biomarkers of awareness in future studies to improve understanding and care for people with severe AD
Bose-Einstein Condensate in Weak 3d Isotropic Speckle Disorder
The effect of a weak three-dimensional (3d) isotropic laser speckle disorder
on various thermodynamic properties of a dilute Bose gas is considered at zero
temperature. First, we summarize the derivation of the autocorrelation function
of laser speckles in 1d and 2d following the seminal work of Goodman. The goal
of this discussion is to show that a Gaussian approximation of this function,
proposed in some recent papers, is inconsistent with the general background of
laser speckle theory. Then we propose a possible experimental realization for
an isotropic 3d laser speckle potential and derive its corresponding
autocorrelation function. Using a Fourier transform of that function, we
calculate both condensate depletion and sound velocity of a Bose-Einstein
condensate as disorder ensemble averages of such a weak laser speckle potential
within a perturbative solution of the Gross-Pitaevskii equation. By doing so,
we reproduce the expression of the normalfluid density obtained earlier within
the treatment of Landau. This physically transparent derivation shows that
condensate particles, which are scattered by disorder, form a gas of
quasiparticles which is responsible for the normalfluid component
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