Atomic layer deposition of Pt@CsH_2PO_4 for the cathodes of solid acid fuel cells

Atomic layer deposition (ALD) has been used to apply continuous Pt films on powders of the solid acid CsH_2PO_4 (CDP), in turn, used in the preparation of cathodes in solid acid fuel cells (SAFCs). The film deposition was carried out at 150 °C using trimethyl(methylcyclopentadienyl)platinum (MeCpPtMe_3) as the Pt source and ozone as the reactant for ligand removal. Chemical analysis showed a Pt growth rate of 0.09 ± 0.01 wt%/cycle subsequent to an initial nucleation delay of 84 ± 20 cycles. Electron microscopy revealed the contiguous nature of the films prepared using 200 or more cycles. The cathode overpotential (0.48 ± 0.02 V at a current density of 200 mA/cm^2) was independent of Pt deposition amount beyond the minimum required to achieve these continuous films. The cell electrochemical characteristics were moreover extremely stable with time, with the cathode overpotentials increasing by no more than 10 mV over a 100 h period of measurement. Thus, ALD holds promise as an effective tool in the preparation of SAFC cathodes with high activity and excellent stability

Differential p53 protein expression in breast cancer fine needle aspirates: the potential for in vivo monitoring

Fine needle aspiration (FNA) biopsy is the least invasive method of sampling breast cancer in vivo and provides material for breast cancer diagnosis. FNA has also been used to examine cellular markers to predict and monitor the effects of therapy. The aim of this study was to assess the accuracy of using FNA material compared with resected cancer for Western blotting studies of the p53 pathway, a key to tumour response to radiotherapy and chemotherapy. Paired samples of breast cancer FNAs collected pre-operatively and post-operatively were compared with tissue samples obtained at the time of surgical resection. Western blots were probed for p53 using the antibodies DO12 and DO1, and for levels of downstream proteins p21/WAF1 and p27. The protein extracted by FNA was sufficient for up to 5 Western blot studies. p53 expression and phosphorylation did not differ significantly pre- and post-operatively, indicating that intra-operative manipulation does not affect p53 expression or downstream activation in breast cancer. However, expression of p53, p21 and p27 varied between individual patients suggesting a range of p53 pathway activation in breast cancer. Immunohistochemistry confirmed that the cancer cells accounted for the protein expression detected on Western blots. FNA yields adequate protein for Western blotting studies and could be used as a method to monitor p53 activity in vivo before and during anti-cancer treatment possibly providing early evidence of tumour response to therapy. © 2001 Cancer Research Campaign  http://www.bjcancer.co

Topographic, Hydraulic, and Vegetative Controls on Bar and Island Development in Mixed Bedrock‐Alluvial, Multichanneled, Dryland Rivers

We investigate processes of bedrock‐core bar and island development in a bedrock‐influenced anastomosed reach of the Sabie River, Kruger National Park (KNP), eastern South Africa. For sites subject to alluvial stripping during an extreme flood event (~4470‐5630 m3 s‐1) in 2012, pre‐ and post‐flood aerial photographs and LiDAR data, 2D morphodynamic simulations, and field observations reveal that the thickest surviving alluvial deposits tend to be located over bedrock topographic lows. At a simulated peak discharge (~4500 m3 s‐1), most sediment (sand, fine gravel) is mobile but localized deposition on bedrock topographic highs is possible. At lower simulated discharges (<1000 m3 s‐1), topographic highs are not submerged, and deposition occurs in lower elevation areas, particularly in areas disconnected from the main channels during falling stage. Field observations suggest that in addition to discharge, rainwash between floods may redistribute sediments from bedrock topographic highs to lower elevation areas, and also highlight the critical role of vegetation colonization in bar stability, and in trapping of additional sediment and organics. These findings challenge the assumptions of preferential deposition on topographic highs that underpin previous analyses of KNP river dynamics, and are synthesized in a new conceptual model that demonstrates how initial bedrock topographic lows become topographic highs (bedrock core‐bars and islands) in the latter stages of sediment accumulation. The model provides particular insight into the development of mixed bedrock‐alluvial anastomosing along the KNP rivers, but similar processes of bar/island development likely occur along numerous other bedrock‐influenced rivers across dryland southern Africa and farther afield

C-terminal diversity within the p53 family accounts for differences in DNA binding and transcriptional activity

The p53 family is known as a family of transcription factors with functions in tumor suppression and development. Whereas the central DNA-binding domain is highly conserved among the three family members p53, p63 and p73, the C-terminal domains (CTDs) are diverse and subject to alternative splicing and post-translational modification. Here we demonstrate that the CTDs strongly influence DNA binding and transcriptional activity: while p53 and the p73 isoform p73γ have basic CTDs and form weak sequence-specific protein–DNA complexes, the major p73 isoforms have neutral CTDs and bind DNA strongly. A basic CTD has been previously shown to enable sliding along the DNA backbone and to facilitate the search for binding sites in the complex genome. Our experiments, however, reveal that a basic CTD also reduces protein–DNA complex stability, intranuclear mobility, promoter occupancy in vivo, target gene activation and induction of cell cycle arrest or apoptosis. A basic CTD therefore provides both positive and negative regulatory functions presumably to enable rapid switching of protein activity in response to stress. The different DNA-binding characteristics of the p53 family members could therefore reflect their predominant role in the cellular stress response (p53) or developmental processes (p73)

Doxorubicin and vinorelbine act independently via p53 expression and p38 activation respectively in breast cancer cell lines

In the treatment of breast cancer, combination chemotherapy is used to overcome drug resistance. Combining doxorubicin and vinorelbine in the treatment of patients with metastatic breast cancer has shown high response rates; even single-agent vinorelbine in patients previously exposed to anthracyclines results in significant remission. Alterations in protein kinase-mediated signal transduction and p53 mutations may play a role in drug resistance with cross-talk between signal transduction and p53 pathways. The aim of this study was to establish the effects of doxorubicin and vinorelbine, as single agents, in combination, and as sequential treatments, on signal transduction and p53 in the breast cancer cell lines MCF-7 and MDA-MB-468. In both cell lines, increased p38 activity was demonstrated following vinorelbine but not doxorubicin treatment, whether vinorelbine was given prior to or simultaneously with doxorubicin. Mitogen-activated protein kinase (MAPK) activity and p53 expression remained unchanged following vinorelbine treatment. Doxorubicin treatment resulted in increased p53 expression, without changes in MAPK or p38 activity. These findings suggest that the effect of doxorubicin and vinorelbine used in combination may be achieved at least in part through distinct mechanisms. This additivism, where doxorubicin acts via p53 expression and vinorelbine through p38 activation, may contribute to the high clinical response rate when the two drugs are used together in the treatment of breast cancer

Atomic layer deposition of Pt@CsH_2PO_4 for the cathodes of solid acid fuel cells

Atomic layer deposition (ALD) has been used to apply continuous Pt films on powders of the solid acid CsH_2PO_4 (CDP), in turn, used in the preparation of cathodes in solid acid fuel cells (SAFCs). The film deposition was carried out at 150 °C using trimethyl(methylcyclopentadienyl)platinum (MeCpPtMe_3) as the Pt source and ozone as the reactant for ligand removal. Chemical analysis showed a Pt growth rate of 0.09 ± 0.01 wt%/cycle subsequent to an initial nucleation delay of 84 ± 20 cycles. Electron microscopy revealed the contiguous nature of the films prepared using 200 or more cycles. The cathode overpotential (0.48 ± 0.02 V at a current density of 200 mA/cm^2) was independent of Pt deposition amount beyond the minimum required to achieve these continuous films. The cell electrochemical characteristics were moreover extremely stable with time, with the cathode overpotentials increasing by no more than 10 mV over a 100 h period of measurement. Thus, ALD holds promise as an effective tool in the preparation of SAFC cathodes with high activity and excellent stability

Intramolecular Energy and Electron Transfer Within a Diazaperopyrenium-Based Cyclophane

Molecules capable of performing highly efficient energy transfer and ultrafast photo-induced electron transfer in well-defined multichromophoric structures are indispensable to the development of artificial photosynthetic systems. Herein, we report on the synthesis, characterization and photophysical properties of a rationally designed multichromophoric tetracationic cyclophane, DAPPBox^(4+), containing a diazaperopyrenium (DAPP^(2+)) unit and an extended viologen (ExBIPY^(2+)) unit, which are linked together by two p-xylylene bridges. Both ^1H NMR spectroscopy and single crystal X-ray diffraction analysis confirm the formation of an asymmetric, rigid, box-like cyclophane, DAPPBox^(4+). The solid-state superstructure of this cyclophane reveals a herringbone-type packing motif, leading to two types of π···π interactions: (i) between the ExBIPY^(2+) unit and the DAPP^(2+) unit (π···π distance of 3.7 Å) in the adjacent parallel cyclophane, as well as (ii) between the ExBIPY^(2+) unit (π···π distance of 3.2 Å) and phenylene ring in the closest orthogonal cyclophane. Moreover, the solution-phase photophysical properties of this cyclophane have been investigated by both steady-state and time-resolved absorption and emission spectroscopies. Upon photoexcitation of DAPPBox^(4+) at 330 nm, rapid and quantitative intramolecular energy transfer occurs from the ^1*ExBIPY^(2+) unit to the DAPP^(2+) unit in 0.5 ps to yield ^1*DAPP^(2+). The same excitation wavelength simultaneously populates a higher excited state of ^1*DAPP^(2+) which then undergoes ultrafast intramolecular electron transfer from ^1*DAPP^(2+) to ExBIPY^(2+) to yield the DAPP^(3+•) – ExBIPY^(+•) radical ion pair in τ = 1.5 ps. Selective excitation of DAPP^(2+) at 505 nm populates a lower excited state where electron transfer is kinetically unfavorable