Decelerated lattice excitation and absence of bulk phonon modes at surfaces: Ultra-fast electron diffraction from Bi(111) surface upon fs-laser excitation.

Ultrafast reflection high-energy electron diffraction is employed to follow the lattice excitation of a Bi(111) surface upon irradiation with a femtosecond laser pulse. The thermal motion of the atoms is analyzed through the Debye-Waller effect. While the Bi bulk is heated on time scales of 2 to 4 ps, we observe that the excitation of vibrational motion of the surface atoms occurs much slower with a time constant of 12 ps. This transient nonequilibrium situation is attributed to the weak coupling between bulk and surface phonon modes which hampers the energy flow between the two subsystems. From the absence of a fast component in the transient diffraction intensity, it is in addition concluded that truncated bulk phonon modes are absent at the surface.

Ultrafast electron diffraction from a Bi(111) surface: Impulsive lattice excitation and Debye-Waller analysis at large momentum transfer.

The lattice response of a Bi(111) surface upon impulsive femtosecond laser excitation is studied with time-resolved reflection high-energy electron diffraction. We employ a Debye-Waller analysis at large momentum transfer of 9.3 Å-1 ≤ Δ k ≤ 21.8 Å-1 in order to study the lattice excitation dynamics of the Bi surface under conditions of weak optical excitation up to 2 mJ/cm2 incident pump fluence. The observed time constants τ int of decay of diffraction spot intensity depend on the momentum transfer Δk and range from 5 to 12 ps. This large variation of τ int is caused by the nonlinearity of the exponential function in the Debye-Waller factor and has to be taken into account for an intensity drop ΔI > 0.2. An analysis of more than 20 diffraction spots with a large variation in Δk gave a consistent value for the time constant τT of vibrational excitation of the surface lattice of 12 ± 1 ps independent on the excitation density. We found no evidence for a deviation from an isotropic Debye-Waller effect and conclude that the primary laser excitation leads to thermal lattice excitation, i.e., heating of the Bi surface.

Ultra-fast electron diffraction at surfaces: from nanoscale heat transport to driven phase transitions.

Many fundamental processes of structural changes at surfaces occur on a pico- or femtosecond time scale. In order to study such ultra-fast processes, we have combined modern surface science techniques with fs-laser pulses in a pump-probe scheme. Reflection high energy electron diffraction (RHEED) with grazing incident electrons ensures surface sensitivity for the probing electron pulses. Utilizing the Debye-Waller effect, we studied the cooling of vibrational excitations in monolayer adsorbate systems or the nanoscale heat transport from an ultra-thin film through a hetero-interface on the lower ps-time scale. The relaxation dynamics of a driven phase transition far away from thermal equilibrium is demonstrated with the In-induced (8×2) reconstruction on Si(111). This surface exhibits a Peierls-like phase transition at 100K from a (8×2) ground state to (4×1) excited state. Upon excitation by a fs-laser pulse, this structural phase transition is driven into an excited (4×1) state at a sample temperature of 20K. Relaxation into the (8×2) ground state occurs after more than 150 ps.

Childlessness and adoption: the experience of loss as a source of suffering.

The present work deals with the issue of child's adoption. Adoption is presented as a difficult (stressful) situation for the adopted child, but also for the childless married couple, who has decided to take in the orphaned child. Adoption as a difficult situation is connected with the experience of loss. The childless spouses experience the loss of their biological parenthood, the loss of their biological child, who died during the prenatal period or just after being born, but also the loss of the status of a "normal" family created in accordance with the normative model of a family. The adopted child, on the other hand, experiences the loss of biological parents and biological siblings, the loss of genealogical continuity and of "the bonds of blood". The child must be confronted with the fact that "one, to be adopted, must be first abandoned". The problem with the studies on adoption lies in their theoretical character. Because of that, the psychological understanding of adoption reality is limited.

Peroxisome proliferator-activated receptor gamma ligands inhibit estrogen biosynthesis in human breast adipose tissue: possible implications for breast cancer therapy.

Estrogen biosynthesis is catalyzed by aromatase cytochrome P-450 (the product of the CYP19 gene). Adipose tissue is the major site of estrogen biosynthesis in postmenopausal women, with the local production of estrogen in breast adipose tissue implicated in the development of breast cancer. In human adipose tissue, aromatase is primarily expressed in the mesenchymal stromal cells and is a marker of the undifferentiated preadipocyte phenotype. Aromatase expression in adipose tissue is regulated via the distal promoter I.4, under the control of glucocorticoids and class I cytokines such as oncostatin M, interleukin 6, and interleukin 11, as well as tumor necrosis factor alpha. These cytokines, which are expressed in adipose, also inhibit adipocyte differentiation. Therefore, we hypothesized that factors which stimulate adipocyte differentiation should inhibit aromatase expression. These factors include synthetic peroxisome proliferator-activated receptor gamma (PPARgamma) ligands such as thiazolidinediones, e.g., troglitazone and rosiglitazone (BRL49653) and the endogenous PPARgamma ligand 15-deoxy-delta12,14-prostaglandin J2. We have demonstrated by measurement of aromatase activity and by reverse transcription-PCR/Southern blotting that these PPARgamma ligands inhibit aromatase expression in cultured breast adipose stromal cells stimulated with oncostatin M or tumor necrosis factor alpha plus dexamethasone in a concentration-dependent manner, whereas a metabolite of troglitazone that does not activate PPARgamma has no effect. We have also shown that troglitazone inhibits luciferase activity of reporter constructs containing various lengths of the upstream region of promoter I.4 transfected into mouse 3T3-L1 preadipocyte mesenchymal cells, whereas the troglitazone metabolite does not. Because local estrogen production in breast fat is implicated in breast cancer development in postmenopausal women, the actions of PPARgamma ligands suggest that they may have potential therapeutic benefit in the treatment and management of breast cancer.

Glass injuries of the hand in children.

One hundred children with glass injuries to the hand were studied with an average follow-up of twenty-two months. Fifty-two had involvement of deep structures. The treatment and results are discussed.

Aluminium foil as a wound dressing.

Aluminium foil has been found to be an extremely useful and painless way of dressing wounds prior to delayed skin grafting. However, it is not recommended for use on skin-graft donor sites as it delays epithelial healing.

Application of ultrasound in assessing burn depth.

Conventional pulse echo ultrasound equipment was modified to provide resolution capable of distinguishing the interfaces in burnt skin. The identification of these interfaces allowed a quantitative assessment of the depth of a burn. Ultrasound is non-invasive and accurate, and so is highly acceptable for clinical use.