6,010 research outputs found
Monomers and dimers of the RepA protein in plasmid pSC101 replication: domains in RepA.
The replication of plasmid pSC101 requires the plasmid-encoded protein RepA. This protein has a double role: it binds to three directly repeated sequences in the pSC101 origin and promotes replication of the plasmid; it binds to two inversely repeated sequences in its promoter region and regulates its own transcription. A series of RepA protein derivatives carrying deletions of the C-terminal region were assayed for specific binding. We found that the last third of the protein is not needed for binding to the various specific sites. Truncated proteins that still bind can also form heterodimers with a wild-type protein. Analysis of band retardation assays conducted with wild-type and truncated proteins indicates that RepA binds to directly repeated sequences as a monomer and to inversely repeated sequences as a dimer
Watching nanomaterials with X-ray eyes: Probing different length scales by combining scattering with spectroscopy
Accretion and photodesorption of CO ice as a function of the incident angle of deposition
Non-thermal desorption of inter- and circum-stellar ice mantles on dust
grains, in particular ultraviolet photon-induced desorption, has gained
importance in recent years. These processes may account for the observed gas
phase abundances of molecules like CO toward cold interstellar clouds. Ice
mantle growth results from gas molecules impinging on the dust from all
directions and incidence angles. Nevertheless, the effect of the incident angle
for deposition on ice photo-desorption rate has not been studied. This work
explores the impact on the accretion and photodesorption rates of the incidence
angle of CO gas molecules with the cold surface during deposition of a CO ice
layer. Infrared spectroscopy monitored CO ice upon deposition at different
angles, ultraviolet-irradiation, and subsequent warm-up. Vacuum-ultraviolet
spectroscopy and a Ni-mesh measured the emission of the ultraviolet lamp.
Molecules ejected from the ice to the gas during irradiation or warm-up were
characterized by a quadrupole mass spectrometer. The photodesorption rate of CO
ice deposited at 11 K and different incident angles was rather stable between 0
and 45. A maximum in the CO photodesorption rate appeared around
70-incidence deposition angle. The same deposition angle leads to the
maximum surface area of water ice. Although this study of the surface area
could not be performed for CO ice, the similar angle dependence in the
photodesorption and the ice surface area suggests that they are closely
related. Further evidence for a dependence of CO ice morphology on deposition
angle is provided by thermal desorption of CO ice experiments
Phasing diffuse scattering. Application of the SIR2002 algorithm to the non-crystallographic phase problem
A new phasing algorithm has been used to determine the phases of diffuse
elastic X-ray scattering from a non-periodic array of gold balls of 50 nm
diameter. Two-dimensional real-space images, showing the charge-density
distribution of the balls, have been reconstructed at 50 nm resolution from
transmission diffraction patterns recorded at 550 eV energy. The reconstructed
image fits well with scanning electron microscope (SEM) image of the same
sample. The algorithm, which uses only the density modification portion of the
SIR2002 program, is compared with the results obtained via the
Gerchberg-Saxton-Fienup HIO algorithm. In this way the relationship between
density modification in crystallography and the HiO algorithm used in signal
and image processing is elucidated.Comment: 7 pages, 12 figure
Stable Determination of the Electromagnetic Coefficients by Boundary Measurements
The goal of this paper is to prove a stable determination of the coefficients
for the time-harmonic Maxwell equations, in a Lipschitz domain, by boundary
measurements
On the evaluation of some three-body variational integrals
Stable recursive relations are presented for the numerical computation of the
integrals
(, and integer, , and real) when the
indices , or are negative. Useful formulas are given for particular
values of the parameters , and .Comment: 12 pages, 1 figure (PS) and 3 tables. Old figures 2 and 3 replaced by
Tables I and III. A further table added. Paper enlarged giving some tips on
the convergence of quadrature
Prevalence of sexual and physical abuse in patients with obstructed defecation: impact on biofeedback treatment
Background: obstructed defecation is one of the most com mon subtypes of constipation, and it is frequently responsive to biofeedback treatment. Aims: since a history of sexual and physical abuse may be pre sent in patients with obstructed defecation, we assessed the inci dence of abuse history in patients with obstructed defecation re ferred to a general gastroenterology practice, and whether such a history may lead to a different outcome of biofeedback training in these patients. Patients and methods: one hundred and twenty-one pa tients (17 men, 104 women, age 53 ± 15 years) with obstructed defecation were studied by retrospective chart review. Their histo ry of sexual, physical and psychological abuse was obtained by a standard interview, and biofeedback training was carried out by means of a three-balloon technique. Results: a history of sexual/physical or psychological abuse was present in 12.4% patients. Biofeedback training yielded a successful improvement of obstructed defecation in 93% patients without abuse and in 100% of patients with abuse; this difference was not statistically different (p = 0.53). Conclusions: the prevalence of sexual/physical or psycholog ical abuse in a population of patients with obstructed defecation referred to a general gastroenterology practice is relatively low; such a history seems not to affect the outcome of biofeedback training in these patients
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