Ballistic Phonons in Ultrathin Nanowires.

According to Fourier's law, a temperature difference across a material results in a linear temperature profile and a thermal conductance that decreases inversely proportional to the system length. These are the hallmarks of diffusive heat flow. Here, we report heat flow in ultrathin (25 nm) GaP nanowires in the absence of a temperature gradient within the wire and find that the heat conductance is independent of wire length. These observations deviate from Fourier's law and are direct proof of ballistic heat flow, persisting for wire lengths up to at least 15 µm at room temperature. When doubling the wire diameter, a remarkably sudden transition to diffusive heat flow is observed. The ballistic heat flow in the ultrathin wires can be modeled within Landauer's formalism by ballistic phonons with an extraordinarily long mean free path.

Phonon Engineering in Twinning Superlattice Nanowires.

One of the current challenges in nanoscience is tailoring the phononic properties of a material. This has long been a rather elusive task because several phonons have wavelengths in the nanometer range. Thus, high quality nanostructuring at that length-scale, unavailable until recently, is necessary for engineering the phonon spectrum. Here we report on the continuous tuning of the phononic properties of a twinning superlattice GaP nanowire by controlling its periodicity. Our experimental results, based on Raman spectroscopy and rationalized by means of ab initio theoretical calculations, give insight into the relation between local crystal structure, overall lattice symmetry, and vibrational properties, demonstrating how material engineering at the nanoscale can be successfully employed in the rational design of the phonon spectrum of a material.

Epidemiology of burns in the Tel Aviv area.

Between 1 August 1988 and 31 January 1992, 421 burn patients were admitted to the Burn Unit at Beilinson Medical Center. Name, age, sex, month of the year, cause of burn, area and degree of burn and duration of stay in hospital were recorded. Of these patients, 37 per cent were treated surgically and the remainder were treated conservatively. The male to female ratio was 2:1. Burns occurred most frequently in July and January; the peak average age was the first decade of life. The most frequent cause in children was scalding (domestic burns), and in adults open fires (work accidents). Patients treated by early tangential excision and skin grafting (204 operations on 157 patients) had a shorter stay in hospital than conservatively treated patients. In accordance with others, we suggest that early surgery of burn injuries decreases morbidity and mortality and leads to better aesthetic results and improved motor function. Secondly, burn injury can be prevented in children and the elderly by increasing safety measures at home, and in adults by enforcing strict safety measures at work.

[Epidemiology and prognostic factors in cutaneous malignant melanoma].

207 patients with primary cutaneous malignant melanoma were admitted between August 1, 1988 and July 31, 1992 for local excision and treatment. The female to male ratio was 1.4:1 and the peak age was in the seventies. The most frequent site in males was the back and in females the legs. Superficial spreading melanoma was the most frequent type (40%); there was also a high rate of nodular melanoma (20%), particularly in males. Thin melanomas accounted for most of the cases. On follow-up 27 (13%) developed metastases in transit or in regional lymph nodes and 10 (5%) developed distant metastases; 2 (1%) had locally recurrent melanoma and 2 died of metastatic melanoma. There was a significant positive correlation between Breslow thickness, Clark's level of invasion, histopathological ulceration, nodular and acral lentiginous type of lesion and development of metastases. These data may be valuable for public and professional education and in the prediction of outcome of melanoma.

Ultrafast non-local control of spontaneous emission.

The radiative interaction of solid-state emitters with cavity fields is the basis of semiconductor microcavity lasers and cavity quantum electrodynamics (CQED) systems. Its control in real time would open new avenues for the generation of non-classical light states, the control of entanglement and the modulation of lasers. However, unlike atomic CQED or circuit quantum electrodynamics, the real-time control of radiative processes has not yet been achieved in semiconductors because of the ultrafast timescales involved. Here we propose an ultrafast non-local moulding of the vacuum field in a coupled-cavity system as an approach to the control of radiative processes and demonstrate the dynamic control of the spontaneous emission (SE) of quantum dots (QDs) in a photonic crystal (PhC) cavity on a ∼ 200 ps timescale, much faster than their natural SE lifetimes.

Cutaneous malignant melanoma in young adults under age 30.

Epidemiologic and clinicopathologic features of malignant melanoma in 129 patients (44 males, 85 females) aged < or = 30 years between 1961 and 1992 were investigated. The number of new young melanoma patients (29 of 216 during the 1960's) declined to 52 of 676 during the 1980's. Predominant sites were legs among females, and head, neck and back among males. Nodular type lesions (56.6%) outnumbered superficial spreading tumors (38.8%). Thirty-one patients (24%) died of melanoma (median survival 2.9 years), with higher male mortality. A decrease in mortality rate was observed over the decades. The relationship between various parameters was analyzed. Nodular lesions were smaller and thicker than superficial spreading lesions, occurred more frequently in males, and carried a worse prognosis (34% mortality) than superficial spreading type tumors (14%); mortality rate was higher for thick (>4 mm) and for large tumor volumes (>300 mm3) vs. thin and small sized lesions, respectively (P = 0.000 for each). Average tumor thickness and volume declined throughout the last three decades. From the data obtained, a typical profile of a young melanoma patient is drawn.

Female breast burns: conservative treatment with a reconstructive aim.

We retrospectively reviewed 421 burn patients treated in our burn unit in the past 3 years, focusing on breast burns in female patients. The aim of our study was to review the epidemiology, establish the mechanism of breast burn occurrence, and review the treatment plan. We evaluated 138 female burn patients, 38 (9%) of whom had non-isolated breast burns. In this group 25 burns (66%) were caused by scalds and 13 (34%) by fire. Scalds were responsible for first- to second-degree burns (50%), and cooking oil and fire for second- to third-degree burns (50%). A statistically significant difference was noted in the incidence of breast burns, which occurred mainly in late summer and fall (P = 0.03). There was a direct correlation between burn depth and duration of hospitalization, with average hospitalization time of 1.45 days for each percent of burn. Most breast burns were domestic, with children constituting the majority of the victims. Most breast burn patients were treated conservatively. Breast deformity on recovery varied in severity from minor deformity correctable with simple breast reduction surgery in older patients to severe deformity requiring further reconstructive surgery in infants.