914 research outputs found
Correlated two-particle scattering on finite cavities
The correlated two-particle problem is solved analytically in the presence of
a finite cavity. The method is demonstrated here in terms of exactly solvable
models for both the cavity as well as the two-particle correlation where the
two-particle potential is chosen in separable form. The two-particle phase
shift is calculated and compared to the single-particle one. The two-particle
bound state behavior is discussed and the influence of the cavity on the
binding properties is calculated.Comment: Derivation shortened and corrected, 14 pages 10 figure
A transfer matrix method for the analysis of fractal quantum potentials
The scattering properties of quantum particles on fractal potentials at
different stages of fractal growth are obtained by means of the transfer matrix
method. This approach can be easily adopted for project assignments in
introductory quantum mechanics for undergraduates. The reflection coefficients
for both the fractal potential and the finite periodic potential are calculated
and compared. It is shown that the reflection coefficient for the fractal has a
self-similar structure associated with the fractal distribution of the
potential
All-fibre source of amplitude-squeezed light pulses
An all-fibre source of amplitude squeezed solitons utilizing the self-phase
modulation in an asymmetric Sagnac interferometer is experimentally
demonstrated. The asymmetry of the interferometer is passively controlled by an
integrated fibre coupler, allowing for the optimisation of the noise reduction.
We have carefully studied the dependence of the amplitude noise on the
asymmetry and the power launched into the Sagnac interferometer. Qualitatively,
we find good agreement between the experimental results, a semi-classical
theory and earlier numerical calculations [Schmitt etl.al., PRL Vol. 81,
p.2446, (1998)]. The stability and flexibility of this all-fibre source makes
it particularly well suited to applications in quantum information science
The hERG channel is dependent upon the Hsp90Îą isoform for maturation and trafficking
Heat shock protein 90 (Hsp90) has emerged as a promising therapeutic target for the treatment of cancer. Several Hsp90 inhibitors have entered clinical trials. However, some toxicological detriments have arisen, such as cardiotoxicity resulting from hERG inhibition following the administration of Hsp90 inhibitors. We sought to investigate this toxicity as hERG has been previously reported as a client protein that depends upon Hsp90 for its maturation and functional trafficking. In this study we show that hERG depends upon a single Hsp90 isoform. hERG preferentially co-immunoprecipitated with Hsp90ι and genetic knockdown of Hsp90ι, but not Hsp90β, resulted in a trafficking-defective hERG channel. This study demonstrates the importance of delineating the isoform dependence of Hsp90 client proteins and provides rationale for the design of isoform-selective Hsp90 inhibitors that avoid detrimental effect
Relationship of hyperlipidemia to comorbidities and lung function in COPD: Results of the COSYCONET cohort
Although hyperlipidemia is common in COPD, its relationship to comorbidities, risk factors and lung function in COPD has not been studied in detail. Using the baseline data of the COSYCONET cohort we addressed this question. Data from 1746 COPD patients (GOLD stage 1â4; mean age 64.6 y, mean FEV1%pred 57%) were evaluated, focusing on the comorbidities hyperlipidemia, diabetes and cardiovascular complex (CVC; including arterial hypertension, cardiac failure, ischemic heart disease). Risk factors comprised age, gender, BMI, and packyears of smoking. The results of linear and logistic regression analyses were implemented into a path analysis model describing the multiple relationships between parameters. Hyperlipidemia (prevalence 42.9%) was associated with lower intrathoracic gas volume (ITGV) and higher forced expiratory volume in 1 second (FEV1) when adjusting for its multiple relationships to risk factors and other comorbidities. These findings were robust in various statistical analyses. The associations between comorbidities and risk factors were in accordance with previous findings, thereby underlining the validity of our data. In conclusion, hyperlipidemia was associated with less hyperinflation and airway obstruction in patients with COPD. This surprising result might be due to different COPD phenotypes in these patients or related to effects of medication
Locale and chemistry of spermine binding in the archetypal inward rectifier Kir2.1
Polyamine block of inwardly rectifying potassium (Kir) channels underlies their steep voltage dependence observed in vivo. We have examined the potency, voltage dependence, and kinetics of spermine block in dimeric Kir2.1 constructs containing one nonreactive subunit and one cysteine-substituted subunit before and after modification by methanethiosulfonate (MTS) reagents. At position 169C (between the D172 ârectification controllerâ and the selectivity filter), modification by either 2-aminoethyl MTS (MTSEA) or 2-(trimethylammonium)ethyl MTS (MTSET) reduced the potency and voltage dependence of spermine block, consistent with this position overlapping the spermine binding site. At position 176C (between D172 and the M2 helix bundle crossing), modification by MTSEA also weakened spermine block. In contrast, MTSET modification of 176C dramatically slowed the kinetics of spermine unblock, with almost no effect on potency or voltage dependence. The data are consistent with MTSET modification of 176C introducing a localized barrier in the inner cavity, resulting in slower spermine entry into and exit from a âdeepâ binding site (likely between the D172 rectification controller and the selectivity filter), but leaving the spermine binding site mostly unaffected. These findings constrain the location of deep spermine binding that underlies steeply voltage-dependent block, and further suggest important chemical details of high affinity binding of spermine in Kir2.1 channelsâthe archetypal model of strong inward rectification
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