Hubert van den Bergh

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The multiphoton dissocn. of 32SF6 was studied in the presence of several inert gases. The reciprocal dissocn. yields increase with increasing total pressure in a nonlinear way for the conditions applied. Different collisional quenching efficiencies were obtained for the various inert gases. From the quenching efficiencies information on the optical pumping process may be obtained.

Clinical results obtained endoscopically with an imaging fluorescence photodetection apparatus based on the use of one excitation wavelength and detection of the fluorescence emission performed in two separate spectral windows are presented. Early cancer photodetection of micro-invasive and in situ carcinoma of the bronchial mucosa after intravenous injection of meso-tetrahydroxyphenylchlorin (m-THPC) was performed during sessions involving photodynamic therapy. Preliminary results are also presented in the

Pyrolytic and photolytic laser chem. vapor deposition of Cu, Pt, Ga, and Sn was studied for the prodn. of low-resistance ohmic contacts of very small dimensions.

The photodissocn. of I2 was studied in the gas phase by laser flash photolysis. The decrease of the quantum yield with increasing C2H5 and C3H8 pressure is interpreted in terms of the cage effect. As the temp. is increased a less pronounced cage effect is obsd. The trends in the measured quantum yields with changing temp. and pressure agree with model calcns. for dissocn. in a viscous continuum. However the simple model applied is not useful for quant. predictions. The 2nd order rate const. for 1 atom recom

Expts. are described on the pyrolytic and photolytic laser chem. vapor deposition (LCVD) of Ga and GaAs, as well as hybrid deposition of the latter. Pyrolytic Ga deposits change in shape with laser power variations. A deposit in the shape of an annulus of .apprx.14 m outside diam. is obsd. at intermediate power densities. The deposited metal is amorphous. Ga photolytic deposits consist of small spheroids 10-20 nm in diam. and a metallic halo around the center of the deposit is again obsd. Both pyrolytic and

Unimol. reactions induced by absorption of multiple quanta of monochromatic IR radiation were studied on a model system comprising dissocn. of CF2HCl giving CF2 and HCl. Three expts. providing detailed information of IR multiphoton chem. were performed which included measurements of the time dependence of the abs. reaction yield during and after the laser pulse, detn. of the av. no. of photons absorbed per mol. of CF2HCl, and measurement of the total reaction yield in strong elec. and magnetic fields.

Fluorescence cystoscopy enhances detection of early bladder cancer. Water used to inflate the bladder during the procedure rapidly contains urine, which may contain fluorochromes. This frequently degrades fluorescence images. Samples of bladder washout flu ...

The abs. :CF2 concn. is measured in situ and in real time by UV-absorption spectroscopy in the IR multiphoton dissocn. of CF2HCl during and after the laser pulse. The :CF2 prodn. rate is measured as a function of the laser intensity and the temp. at 9.17 mm. This rate increases with the IR intensity and temp. for nearly the whole range of conditions applied. At the highest temps. attained the :CF2 prodn. rates start to decrease with increasing temp.

Particle size should be optimized to achieve targeted and extended drug delivery to the affected tissues. We describe here the effects of the mean particle size on the pharmacokinetics and photothrombic activity of meso-tetra(carboxyphenyl)porphyrin (TCPP) ...

The low pressure chem. vapor deposition (LPCVD) of Cu from its bis-hexafluoroacetylacetonate was studied on oxidized Si substrates partially covered with a Pt seeding layer. With a known concn. of water vapor in the gas mixt., almost equal Cu film growth rates were obtained when using either H or He as carrier gas. For both carrier gases, an increase of the Cu growth rate was obsd. with an increasing amt. of water vapor added to the gas mixt., and deposition rates above 500 .ANG./min were obtained. The chem

A new indicator is proposed to det. whether tropospheric O3 prodn. in a specific area is limited by volatile org. compds. (VOC) or NOx. This indicator, tVOCOH/tNOxOH, describes the ratio of OH- lifetime vs. losses by reaction with VOC and NOx. Whereas tNOxOH can be obtained by conventional measurements, the new pump and probe OH approach makes it possible to also obtain tVOCOH. Indicator values above a threshold value of 0.2 +- 50% are representative of NOx-satd. conditions, where an increase of NOx emissio

Diamond growth on a (100) oriented Si substrate by a laser-induced chem. transport reaction (LICTR) method is described. SEM indicated that the LICTR-deposited diamonds had a cubic structure. Their Raman spectrum obsd. at Stokes shifts between 1300 and 1370 cm-1 showed a single sharp line with the position and full width at half-max. very close to those of natural diamond. These results contrast with those obtained for diamond produced by hot-filament CVD.

Autofluorescence bronchoscopy (AFB) is a highly sensitive tool for the detection of early bronchial cancers. However, its specificity remains limited due to primarily false positive results induced by hyperplasia, metaplasia and inflammation. We have inves ...

Thin Cu layers were prepd. via MOCVD from volatile pyrazolylboratoCu(I) complexes. Expts. involved CVD in a low pressure reactor between 150-350 Deg in H2/N2/He mixts. were carried out. Substrate temp., source temp. and gas compn. were varied to obtain the optimum growth rate. The Cu layers were characterized by optical microscopy and SEM, XRD, and WDX. The metallic nature of the deposited films was proved by a four-point-probe measurement of the elec. resistivity. A selective deposition on metal seeded sur

The laser chem. vapor deposition of platinum from its bishexafluoroacetylacetonate deriv. is studied with a cw Ar ion laser at 458 and 514 nm. The height, the width, as well as the elec. cond. of the deposited stripes are reported as a function of the vapor pressure of the metalorg. precursor, the laser intensity, and the writing speed.

PURPOSE: To optimize conditions for photodynamic detection (PDD) and photodynamic therapy (PDT) of bladder carcinoma, urothelial accumulation of protoporphyrin IX (PpIX) and conditions leading to cell photodestruction were studied. MATERIALS AND METHODS: Porcine and human bladder mucosae were superfused with derivatives of 5-aminolevulinic acid (ALA). PpIX accumulation and distribution across the mucosa was studied by microspectrofluorometry. Cell viability and structural integrity were assessed by using vi

The optimal drug-light interval for effective photodynamic therapy (PDT) of early squamous cell carcinomas was evaluated with tetra(m-hydroxyphenyl)chlorin (mTHPC) by means of two complementary modalities: irradiation tests and ex vivo fluorescence microsc ...

A new way of measuring ozone and water vapor in the Planetary Boundary Layer (PBL) is proposed. The method is based on the simultaneous measurement of the Raman backscattering in the UV by O2, N2 and H2O, using a single pump beam at 266 nm. The ozone concentration is retrieved from the differential absorption of the N2 and O2 Raman backscattered signals, while the water vapor is measured using the classical Raman scheme. We present some preliminary results showing daytime ozone measurements in good correlat

A combined measurement of O3 concn. and wind speed by lidar is presented, which permits a flux detn. of this pollutant. Measurements were obtained using a shot per shot differential absorption lidar (DIAL) system in which each return is recorded, stored, and treated allowing the study of the temporal evolution of the signal. O3 and wind range resolved measurements are key variables of simulations used to analyze photochem. smog episodes. Results demonstrated that the usual detn. of static O3 concns. can be

The infrared multiphoton dissociation of chlorodifluoromethane is studied in a dc electric field. The reaction yield is measured as a function of the laser energy fluence, the CF2HCl pressure, and the electric field strength in the range 0⩽E⩽5.4 kV cm−1. At low fluence (F

Hubert van den Bergh

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Pressure dependence in the multiphoton dissociation of sulfur-32 hexafluoride

Fluorescence imaging photodetection of early cancer in the bronchi with mTHPC and in the bladder with ALA-induced protoporphyrin IX: preliminary clinical results

Laser induced chemical vapor deposition of metals for electrical contacts in semiconductor processing

The temperature dependence of the cage effect in the gas phase

Laser chemical vapor deposition of gallium and gallium arsenide

Infrared multiphoton chemistry: some recent developments

Optical spectroscopy of the bladder washout fluid to optimize fluorescence cystoscopy with Hexvix

An investigation of laser intensity and temperature effects in the time-resolved infrared multiphoton dissociation of chlorodifluoromethane

Effect of nanoparticle size on the extravasation and the photothrombic activity of meso(p-tetracarboxyphenyl)porphyrin

Selective low pressure chemical vapor deposition of copper: effect of added water vapor in hydrogen or helium carrier gas

Total VOC reactivity in the planetary boundary layer 2. A new indicator for determining the sensitivity of the ozone production to VOC and NOx

A laser-induced chemical transport reaction method for diamond deposition

Improvement of the specificity of cancer detection by autofluorescence imaging in the tracheo-bronchial tree using backscattered violet light

Investigation and characterization of thin MOCVD copper films from pyrazolylboratocopper(I) complexes

Growth rates and electrical conductivity of microscopic ohmic contacts fabricated by laser chemical vapor deposition of platinum

Optimisation of the formation and distribution of protoporphyrin IX in the urothelium: An in vitro approach

Photodynamic therapy of early squamous cell carcinoma with tetra(m-hydroxyphenyl)chlorin: optimal drug-light interval

A Raman differential absorption lidar for ozone and water vapor measurement in the lower troposphere

Ozone flux determination with a shot per shot DIAL instrument during the MEDCAPHOT field campaign

Electric field effects in the infrared multiphoton dissociation of CF2HCl