We describe a simple methodology for the effective retrieval of Raman spectra of subsurface layers in diffusely scattering media. The technique is based on the collection of Raman scattered light from surface regions that are laterally offset away from the excitation laser spot on the sample. The Raman spectra obtained in this way exhibit a variation in relative spectral intensities of the surface and subsurface layers of the sample being investigated. The data set is processed using a multivariate data analysis to yield pure Raman spectra of the individual sample layers, providing a method for the effective elimination of surface Raman scatter. The methodology is applicable to the retrieval of pure Raman spectra from depths well in excess of those accessible with conventional confocal microscopy. In this first feasibility study we have differentiated between surface and subsurface Raman signals within a diffusely scattering sample composed of two layers: trans-stilbene powder beneath a 1 mm thick over-layer of PMMA (poly(methyl methacrylate)) powder. The improvement in contrast of the subsurface trans-stilbene layer without numerical processing was 19 times. The potential applications include biomedical subsurface probing of specific tissues through different overlying tissues such as assessment of bone quality through skin, providing an effective noninvasive means of screening for bone degeneration, other skeletal disease diagnosis, and dermatology studies, as well as materials and catalyst research.

Using a laser tweezers method, we have determined the long-range repulsive force as a function of separation between two charged, spherical polystyrene particles (2.7 microm diameter) present at a nonpolar oil-water interface. At large separations (6 to 12 microm between particle centers) the force is found to decay with distance to the power -4 and is insensitive to the ionic strength of the aqueous phase. The results are consistent with a model in which the repulsion arises primarily from the presence of a very small residual electric charge at the particle-oil interface. This charge corresponds to a fractional dissociation of the total ionizable (sulfate) groups present at the particle-oil surface of approximately 3 x 10(-4).

Charge-transfer excited states have frequently been studied by using 4-dimethylaminobenzonitrile (DMABN) as a model. In nonpolar solvents, a single fluorescence band is observed from a locally excited (LE) state. In polar solvents, the initially populated LE state reacts further to produce a stable intramolecular charge-transfer (ICT) state, which gives rise to a second fluorescence band that overlaps with, but is abnormally red-shifted from, the LE emission.[1] Results of experiments using aprotic solvents are well described by models in which polarity is the only solvent property that affects the charge transfer reaction activation energy and the relative stabilization of the ICT and LE states.[2] Whilst much work continues to concentrate on determining the structures of the LE and ICT states, [3][4][5][6][7] the precise nature of the difference between the properties of the excited state in protic and aprotic solvents is little understood. For example, the fluorescence quantum yield of DMABN in protic solvents is lower and the fluorescence spectrum is further red-shifted and broadened, relative to measurements in aprotic solvents of the same polarity, [8,9] and the fluorescence decay kinetics are difficult to interpret.[2] Hydrogen bonding in protic solvents can lead to complicated interactions [10] but although specific solute-solvent and solute-solute interactions have been discussed, [8,[11][12][13][14] there is no generally accepted explanation. There are similar problems in other cases of dual fluorescence.[15]The time-resolved infrared (TRIR) absorption spectra presented here demonstrate and monitor the formation of a hydrogen-bonded charge-transfer state of photoexcited DMABN in the protic solvent methanol (MeOH), through the development of the CN IR absorption band from an initial singlet into a doublet. The initial single band is interpreted as belonging to an ICT state like that created in aprotic acetonitrile (MeCN), where only one absorption band is observed at all delay times. The second component is interpreted as being due to the hydrogen-bonded chargetransfer state; the kinetics show the populations of the free and hydrogen-bonded species coming to dynamic equilibrium. We designate the hydrogen-bonded state as HICT. This is the first direct observation of hydrogen bonding in an excited state. Since the populations in the LE state and the two charge-transfer states coexist, the fluorescence will be triple, not dual in character. Neglect of this major factor is considered to account for much of the difficulty in interpreting the fluorescence results. [2,8,[11][12][13] A mechanism of this kind has not to our knowledge been proposed before. We believe this interpretation is applicable to other molecules with solvent-dependent dual fluorescence. Figure 1 shows TRIR spectra of DMABN in MeCN (a) and MeOH (b) recorded with sub-picosecond time resolution at pump-probe delays from 2 to 3000 ps after excitation; Figure 2 gives the time-dependence of the absorption band areas. Kinetics parameters were dete...

BackgroundAcute hospital services account for the largest proportion of health care system budgets, and older adults are the most frequent users. As a result, older people who have been recently discharged from hospital may be at greater risk of readmission. This study aims to evaluate the comparative effectiveness of transitional care interventions on unplanned hospital readmissions within 28 days, 12 weeks and 24 weeks following hospital discharge.MethodThe present study was a randomised controlled trial (ACTRN12608000202369). The trial involved 222 participants who were recruited from medical wards in two metropolitan hospitals in Australia. Participants were eligible for inclusion if they were aged 65 years and over, admitted with a medical diagnosis and had at least one risk factor for readmission. Participants were randomised to one of four groups: standard care, exercise program only, Nurse Home visit and Telephone follow-up (N-HaT), or Exercise program and Nurse Home visit and Telephone follow-up (ExN-HaT). Socio-demographics, health and functional ability were assessed at baseline, 28 days, 12 weeks and 24 weeks. The primary outcome measure was unplanned hospital readmission which was defined as any hospital admission for an unforeseen or unplanned cause.ResultsParticipants in the ExN-HaT or the N-HaT groups were 3.6 times and 2.6 times respectively significantly less likely to have an unplanned readmission 28 days following discharge (ExN-HaT group HR 0.28, 95% CI 0.09–0.87, p = 0.029; N-HaT group HR 0.38, 95% CI 0.13–1.07, p = 0.067). Participants in the ExN-HaT or the N-HaT groups were 2.13 and 2.63 times respectively less likely to have an unplanned readmission in the 12 weeks after discharge (ExN-HaT group HR 0.47, 95% CI 0.23–0.97, p = 0.014; N-HaT group HR 0.38, 95% CI 0.18–0.82, p = 0.040). At 24 weeks after discharge, there were no significant differences between groups.ConclusionMultifaceted transitional care interventions across hospital and community settings are beneficial, with lower hospital readmission rates observed in those receiving more transitional intervention components, although only in first 12 weeks.Trial registrationAustralian and New Zealand Clinical Trial Registry (ACTRN12608000202369).