A high sensitivity ultralow temperature RF conductance and noise measurement setup

We report on the realization of a high sensitivity RF noise measurement scheme to study small current fluctuations of mesoscopic systems at milli-Kelvin temperatures. The setup relies on the combination of an interferometric amplification scheme and a quarter-wave impedance transformer, allowing the measurement of noise power spectral densities with gigahertz bandwidth up to five orders of magnitude below the amplifier noise floor. We simultaneously measure the high frequency conductance of the sample by derivating a portion of the signal to a microwave homodyne detection. We describe the principle of the setup, as well as its implementation and calibration. Finally, we show that our setup allows to fully characterize a subnanosecond on-demand single electron source. More generally, its sensitivity and bandwidth make it suitable for applications manipulating single charges at GHz frequencies.

[High resolution MR imaging of the skin: normal imaging features]

PURPOSE

To describe the qualitative and quantitative MR imaging features of normal skin.

MATERIALS AND METHODS

Thirty-one normal subjects underwent MR evaluation on a 1.5 Tesla magnet using a dedicated coil. Several skin sites were evaluated (back at the scapular level, posterior calf and inferior heel). Two pulse sequences were acquired: a SE T1W and a gradient-echo sequence (FIESTA). Qualitative and quantitative analysis was performed for all three sites.

RESULTS

In normal subjects, the different skin layers (callus, epidermis, dermis, hypodermis and pilosebaceous follicles) can be separated and measured on MR. Epidermis and hypodermis are hyperintense whereas dermis is hypointense. Our results confirm the presence of qualitative and quantitative variations between different skin regions. In some cases, a differentiation between papillary and reticular dermis can be achieved. Pilosebaceous follicles and the deep vascular network were clearly depicted on the FIESTA sequence. Measurements for each skin layer were compared based on sex, site and MR pulse sequence.

CONCLUSION

MRI provides evaluation of the different skin layers, epidermis, dermis, and hypodermis, and their different components.

[Shoulder radiography: useful radiographic views in current practice]

The purposes of this paper are: 1) to review the different radiographic projections commonly used to explore shoulder pathology; 2) to propose a practical approach for radiographic evaluation of the shoulder, adapted to the main clinical situations; 3) to recognize the different imaging features of the most frequent shoulder diseases.

Discovery of new Gram-negative antivirulence drugs: structure and properties of novel E. coli WaaC inhibitors

Heptosyltransferases such as WaaC represent promising and attractive targets for the discovery of new Gram-negative antibacterial drugs based on antivirulence mechanisms. We report herein our approach to the identification of the first micromolar inhibitors of WaaC and the preliminary SAR generated from this family of 2-aryl-5-methyl-4-(5-aryl-furan-2-yl-methylene)-2,4-dihydro-pyrazol-3-ones identified by virtual screening.

A new long-chain UV absorber derived from 4-tert-butyl-4'-methoxydibenzoylmethane: absorbance stability under solar irradiation

A new UV filter, the 1-(4-tert-butylphenyl)-2-decanyl-3-(4'-methoxyphenyl)-propane 1,3-dione called C10-DBM, was prepared by grafting a ten-carbon aliphatic chain to the alpha-carbonyl position of 4- tert -butyl-4'-methoxydibenzoylmethane (BM-DBM).(1) UVA absorption efficiency of a cosmetic preparation containing this new filter, called C10-DBM, was tested and compared to an identical preparation containing BM-DBM. The two preparations were irradiated under a 150-W xenon lamp or exposed to natural sunlight. The originality of this new filter resided in that its UVA absorbance appeared during the irradiation of the molecule. Moreover, although the molar absorption coefficient of C10-DBM in the UVA domain was lower than that of BM-DBM, its absorption showed much more photostable behavior under both methods of irradiation. After two hours of sunlight exposure, the preparation containing the BM-DBM lost 85% of its UVA absorbance, whereas the UVA absorbance of the preparation containing C10-DBM showed a decrease of 3% in comparison to the maximum absorbance obtained after 30 minutes of irradiation. Also, after two hours of exposure to natural sunlight, the UVA absorbance of the preparation containing C10-DBM remained above its initial value (before the irradiation began).

Comparative expression of vascular endothelial growth factor family members, VEGF-B, -C and -D, by normal human keratinocytes and fibroblasts

The vascular endothelial growth factor (VEGF) family includes the related polypeptides VEGF-B, -C and -D, which contribute to endothelial and lymphatic vessel development. The parental VEGF molecule, VEGF-A, has been widely described in the skin, but the other members of the VEGF family have not yet been reported. The aim of our study was to determine whether the two main skin cells, keratinocytes and fibroblasts, expressed VEGF-B, -C and -D in basal condition and after stimulation by either growth factors or the pro-inflammatory cytokine tumour necrosis factor-alpha (TNF-alpha). Reverse-transcription polymerase chain reaction (RT-PCR) analysis on cultured normal human keratinocytes (NHKs) and normal human fibroblasts (NHFs) allowed the detection of different levels of VEGF-B, -C and -D mRNA, in both cell types with similar RT-PCR products in the skin cells. A semi-quantitative evaluation of the VEGF family proteins by dot blot, using the different human recombinant VEGFs, showed different levels of VEGF-B, -C and -D, in NHKs and NHFs. After cell stimulation by growth factors (epidermal growth factor (EGF) and transforming growth factor-beta1 (TGF-beta1) for NHKs and NHFs, respectively), a significant up-regulation of the VEGF family member proteins was observed in NHFs but not in NHKs. Conversely, TNF-alpha did not exert a significant effect. However, we could not detect any transcriptional modification in stimulated cells, whatever the stimulation duration. The addition of cycloheximide to the cell cultures strongly inhibited the increase of VEGF proteins in TGF-beta1-stimulated NHFs. Taken together, the results underline the major role played by NHFs in the elaboration of the VEGF family proteins known to regulate wound healing, chronic inflammation and tumour angiogenesis and lymphangiogenesis.

[Risk factors for amoxicillin-clavulanate-resistant Escherichia coli in ICU patients]

OBJECTIVE

To determine risk factors of infections with amoxicillin-clavulanate-resistant Escherichia coli in ICU patients.

STUDY DESIGN

Prospective, consecutive sample survey study.

PATIENTS

A consecutive series of 133 patients from whom culture results were positive for E. coli during their ICU stay.

METHODS

Risk factors analysed included demographics, comorbid conditions, and antimicrobial drug exposure. Univariate and multivariate analysis were performed.

RESULTS

Multivariate logistic regression analysis identified only one significant independent factor associated with the emergence of amoxicillin-clavulanate-resistant E. coli: prior use of amoxicillin (odds ratio: 5.45).

CONCLUSION

Clinicians should avoid administering amoxicillin-clavulanate as empiric therapy for possible E. coli infection in patients that have recently been treated with amoxicillin.

IL-4 and interferon-gamma differentially modulate vascular endothelial growth factor release from normal human keratinocytes and fibroblasts

IL-4 and interferon-gamma (IFN-gamma) are crucial modulators of the immune system and are reported as active antitumor agents and potent inhibitors of angiogenesis. We investigated the effects of these two cytokines on the expression of vascular endothelial growth factor (VEGF), a mediator of major importance in the angiogenesis associated with inflammation, wound healing and tumor invasion and expressed by activated keratinocytes and dermal fibroblasts. Human keratinocytes (HK) and fibroblasts (HF) derived from foreskins, were further cultured during 24 h in defined medium, supplemented or not with the selected growth factors, EGF and TGF-beta1, respectively, before receiving the addition of either IL-4 or IFN-gamma during 24 and 48 h. In basal conditions, fibroblasts produced smaller amounts of VEGF than keratinocytes; the addition of growth factors to the skin cells induced a drastic increase of VEGF secretion. In HF, the basal level of VEGF secretion was reduced by IFN-gamma and slightly increased by IL-4 whereas in HK, IFN-gamma enhanced the secretion of VEGF after 48 h and IL-4 either tended to reduce VEGF secretion or did not exert any effect. Similar but more significant results were observed in skin cells activated by growth-stimulating factors. The association of IL-4 and IFN-gamma mimicked the effects of IFN-gamma alone both in HF and HK. Taken together, these results indicate opposite effects of IFN-gamma and IL-4 on VEGF expression from normal and activated HF and HK. IL-4 may be considered as a poor modulator of VEGF secretion by dermal and epidermal cells. Conversely, IFN-gamma appears as a prominent and versatile mediator in the desregulated angiogenesis associated with inflammatory skin reactions characterized by a T-helper type 1 cell-mediated response.