Orbital photogalvanic effects in quantum-confined structures

We report on the circular and linear photogalvanic effects caused by free-carrier absorption of terahertz radiation in electron channels on (001)-oriented and miscut silicon surfaces. The photocurrent behavior upon variation of the radiation polarization state, wavelength, gate voltage and temperature is studied. We present the microscopical and phenomenological theory of the photogalvanic effects, which describes well the experimental results. In particular, it is demonstrated that the circular (photon-helicity sensitive) photocurrent in silicon-based structures is of pure orbital nature originating from the quantum interference of different pathways contributing to the absorption of monochromatic radiation.Comment: 8 pages, 5 figures, two culumne

Chemical analysis of pottery demonstrates prehistoric origin for high-altitude alpine dairying

The European high Alps are internationally renowned for their dairy produce, which are of huge cultural and economic significance to the region. Although the recent history of alpine dairying has been well studied, virtually nothing is known regarding the origins of this practice. This is due to poor preservation of high altitude archaeological sites and the ephemeral nature of transhumance economic practices. Archaeologists have suggested that stone structures that appear around 3,000 years ago are associated with more intense seasonal occupation of the high Alps and perhaps the establishment of new economic strategies. Here, we report on organic residue analysis of small fragments of pottery sherds that are occasionally preserved both at these sites and earlier prehistoric rock-shelters. Based mainly on isotopic criteria, dairy lipids could only be identified on ceramics from the stone structures, which date to the Iron Age (ca. 3,000 - 2,500 BP), providing the earliest evidence of this practice in the high Alps. Dairy production in such a marginal environment implies a high degree of risk even by today’s standards. We postulate that this practice was driven by population increase and climate deterioration that put pressure on lowland agropastoral systems and the establishment of more extensive trade networks, leading to greater demand for highly nutritious and transportable dairy products

Polyurethane scaffold with in situ swelling capacity for nucleus pulposus replacement

Nucleus pulposus (NP) replacement offers a minimally invasive alternative to spinal fusion or total disc replacement for the treatment of intervertebral disc (IVD) degeneration. This study aimed to develop a cytocompatible {NP} replacement material, which is feasible for non-invasive delivery and tunable design, and allows immediate mechanical restoration of the IVD. A bi-phasic polyurethane scaffold was fabricated consisting of a core material with rapid swelling property and a flexible electrospun envelope. The scaffold was assessed in a bovine whole {IVD} organ culture model under dynamic load for 14 days. Nucleotomy was achieved by incision through the endplate without damaging the annulus fibrosus. After implantation of the scaffold and in situ swelling, the dynamic compressive stiffness and disc height were restored immediately. The scaffold also showed favorable cytocompatibility for native disc cells. Implantation of the scaffold in a partially nucleotomized {IVD} down-regulated catabolic gene expression, increased proteoglycan and type {II} collagen intensity and decreased type I collagen intensity in remaining {NP} tissue, indicating potential to retard degeneration and preserve the {IVD} cell phenotype. The scaffold can be delivered in a minimally invasive manner, and the geometry of the scaffold post-hydration is tunable by adjusting the core material, which allows individualized design. Keywords : Intervertebral disc degeneratio

Thermally Triggered Hydrogel Injection Into Bovine Intervertebral Disc Tissue Explants Induces Differentiation Of Mesenchymal Stem Cells And Restores Mechanical Function.

We previously reported a synthetic Laponite® crosslinked pNIPAM-co-DMAc (L-pNIPAM-co-DMAc) hydrogel which promotes differentiation of mesenchymal stem cells (MSCs) to nucleus pulposus (NP) cells without additional growth factors. The clinical success of this hydrogel is dependent on: integration with surrounding tissue; the capacity to restore mechanical function; as well as supporting the viability and differentiation of delivered MSCs. Bovine NP tissue explants were injected with media (control), human MSCs (hMSCs) alone, acellular L-pNIPAM-co-DMAc hydrogel or hMSCs incorporated within the L-pNIPAM-co-DMAc hydrogel and maintained at 5% O2 for 6 weeks. Viability of native NP cells and delivered MSCs was maintained. Furthermore hMSCs delivered via the L-pNIPAM-co-DMAc hydrogel differentiated and produced NP matrix components: aggrecan, collagen type II and chondroitin sulphate, with integration of the hydrogel with native NP tissue. In addition L-pNIPAM-co-DMAc hydrogel injected into collagenase digested bovine discs filled micro and macro fissures, were maintained within the disc during loading and restored IVD stiffness. The mechanical support of the L-pNIPAM-co-DMAc hydrogel, to restore disc height, could provide immediate symptomatic pain relief, whilst the delivery of MSCs over time regenerates the NP extracellular matrix; thus the L-pNIPAM-co-DMAc hydrogel could provide a combined cellular and mechanical repair approach

In vivo biofunctional evaluation of hydrogels for disc regeneration

Purpose Regenerative strategies aim to restore the original biofunctionality of the intervertebral disc. Different biomaterials are available, which might support disc regeneration. In the present study, the prospects of success of two hydrogels functionalized with anti-angiogenic peptides and seeded with bone marrow derived mononuclear cells (BMC), respectively, were investigated in an ovine nucleotomy model. Methods In a one-step procedure iliac crest aspirates were harvested and, subsequently, separated BMC were seeded on hydrogels and implanted into the ovine disc. For the cell-seeded approach a hyaluronic acid-based hydrogel was used. The anti-angiogenic potential of newly developed VEGF-blockers was investigated on ionically crosslinked metacrylated gellan gum hydrogels. Untreated discs served as nucleotomy controls. 24 adult merino sheep were used. After 6 weeks histological, after 12 weeks histological and biomechanical analyses were conducted. Results Biomechanical tests revealed no differences between any of the implanted and nucleotomized discs. All implanted discs significantly degenerated compared to intact discs. In contrast, there was no marked difference between implanted and nucleotomized discs. In tendency, albeit not significant, degeneration score and disc height index deteriorated for all but not for the cell-seeded hydrogels from 6 to 12 weeks. Cell-seeded hydrogels slightly decelerated degeneration. Conclusions None of the hydrogel configurations was able to regenerate biofunctionality of the intervertebral disc. This might presumably be caused by hydrogel extrusion. Great importance should be given to the development of annulus sealants, which effectively exploit the potential of (cell-seeded) hydrogels for biological disc regeneration and restoration of intervertebral disc functioningThis work was supported by the EU-project Disc Regeneration (NMP3-LA-2008-213904). Technical assistance of Iris Baum and the whole animal surgery team of the Institute of Orthopaedic Research and Biomechanics, Ulm, are gratefully acknowledged. DDAHA hydrogels were kindly provided by Cristina Longinotti (DDAHA, Anika Therapeutics, Abano Therme, Italy)

Observation of orbital circular photogalvanic effect

We report on the observation of the circular photogalvanic effect in Si-metal-oxide-semiconductor fieldeffect transistors with inversion channel excited by terahertz radiation. We demonstrate that in spite of the fact that the photocurrent is caused by transfer of the photon angular momentum to free carriers, it is not due to spin orientation but has a pure orbital origin. It results from the quantum interference of different pathways contributing to the free-carrier absorption of monochromatic radiation

High impact: early pastoralism and environmental change during the Neolithic and Bronze Age in the Silvretta Alps (Switzerland/Austria) as evidenced by archaeological, palaeoecological and pedological proxies

The beginnings of the continuous human presence and of pastoral activities in the high mountainous region of Central Europe have recently become a frequently discussed topic in both archaeology and palaeoecology. In extreme environments such as the high Alpine main ridge and adjacent areas, highly adaptive subsistence strategies were required to exploit natural resources available in the subalpine and alpine zones. Such strategies were determined by changing environmental, social, and economic conditions. To investigate the relationships between settlement dynamics, human impact, and Holocene climatic changes, we studied the valleys of the Silvretta Massif in the central Eastern Alps between the Paznaun(Austria) and Lower Engadine valleys (Switzerland). We are presenting new archaeological, palaeoecological, and pedological evidence of continuous human activities from the Early Neolithic Period to the Bronze Age (~ 5,500–800 BC). This evidence sheds new light on the beginnings of intensified human impact on the high mountainous landscape, i.e. activities beyond Mesolithic hunting along the timberline. Archaeological data suggest a shift in subsistence strategies from hunting to herding at the end of the Neolithic Period (~ 2,800–2,500 BC). While palaeoecological data confirm this trend, they also indicate potentially earlier human and livestock impact through forest clearances by fire and grazing from about 4,200 BC onwards. In addition to archaeological sites and peat bogs, soils in high-altitude regions prove to be appropriate archives indicating former vegetation cover, shifts of timberline altitudes as well as disturbance of soil formation by human activity such as by slash-and-burn and by livestock grazing.Palaeobotan