Efficient Green Emission from Wurtzite Al xIn1- xP Nanowires.

Direct band gap III-V semiconductors, emitting efficiently in the amber-green region of the visible spectrum, are still missing, causing loss in efficiency in light emitting diodes operating in this region, a phenomenon known as the "green gap". Novel geometries and crystal symmetries however show strong promise in overcoming this limit. Here we develop a novel material system, consisting of wurtzite Al xIn1- xP nanowires, which is predicted to have a direct band gap in the green region. The nanowires are grown with selective area metalorganic vapor phase epitaxy and show wurtzite crystal purity from transmission electron microscopy. We show strong light emission at room temperature between the near-infrared 875 nm (1.42 eV) and the "pure green" 555 nm (2.23 eV). We investigate the band structure of wurtzite Al xIn1- xP using time-resolved and temperature-dependent photoluminescence measurements and compare the experimental results with density functional theory simulations, obtaining excellent agreement. Our work paves the way for high-efficiency green light emitting diodes based on wurtzite III-phosphide nanowires.

[Quality of life and depression in hearing-impairment : A German survey]. / Lebensqualität und Depression bei Hörminderung : Eine deutsche Bedarfsanalyse.

BACKGROUND: Hearing-impairment can lead to a reduced quality of life and thus represents a vulnerability factor for mental disorders. OBJECTIVE: This study represents the first psychiatric analysis of subjective quality of life and depression in people with hearing-impairment in Germany. MATERIALS AND METHODS: The patient group included 30 hearing-impaired participants (27 women, 3 men) with a current or previous mental disorder and/or psychiatric/psychotherapeutic treatment (age: mean, M = 49.67 years; standard deviation, SD = 13.54 years). The control group consisted of 22 hearing-impaired participants (16 women, 6 men) without mental disorders or treatment (age: M = 52.41 years, SD = 17.30 years). Besides sociodemographic variables, we registered onset/extent of the various hearing-impairments and hearing aid provision. Both groups underwent extensive diagnostic assessment comprising subjective functional impairment (Sheehan Disability Scale, SDS), health-related quality of life (SF-36 Health Survey), and depressive symptoms (Beck Depression Inventory, BDI-II). RESULTS: Groups did not differ significantly in terms of sociodemographic variables such as age, gender, or intelligence. Participants of the patient group had a significantly greater subjective impairment, a lower quality of life, and more pronounced symptoms of depression. The invasiveness of the hearing aid (i. e., cochlear implant) as well as the timepoint of hearing-impairment onset (postlingually) appear to serve as vulnerability factors for mental health problems in this group. CONCLUSION: Our results indicate that besides delivering high-quality acoustic care, practitioners should continuously check patients' requirements for psychosocial treatment due to a loss of quality of life. The development of a specific psychotherapeutic treatment for hearing-impaired clients requires additional research focused on protective and vulnerability factors which may influence the emergence of mental disorders in these patients.

Photon bunching in cathodoluminescence.

We have measured the second order correlation function [g^{(2)}(τ)] of the cathodoluminescence intensity resulting from the excitation by fast electrons of defect centers in wide band-gap semiconductor nanocrystals of diamond and hexagonal boron nitride. We show that the cathodoluminescence second order correlation function g^{(2)}(τ) of multiple defect centers is dominated by a large, nanosecond zero-delay bunching (g^{(2)}(0)>30), in stark contrast to their flat photoluminescence g^{(2)}(τ) function. We have developed a model showing that this bunching can be attributed to the synchronized emission from several defect centers excited by the same electron through the deexcitation of a bulk plasmon into few electron-hole pairs.

[Universal newborn hearing screening : Definition of uniform parameters by the Association of German Hearing Screening Centers as a requirement for nationwide evaluation with valid results]. / Universelles Neugeborenen-Hörscreening : Definition einheitlicher Parameter durch den Verband Deutscher Hörscreening-Zentralen (VDHZ) als Voraussetzung für eine flächendeckende Evaluation mit validen Ergebnissen.

BACKGROUND: Since 2009, all newborns in Germany have been entitled to universal neonatal hearing screening (UNHS). UNHS with tracking of test results leads to earlier detection of hearing disorders. The Association of German Hearing Screening Centers (Verband Deutscher Hörscreening-Zentralen, VDHZ) was founded to promote nationwide tracking, validity and quality control of UNHS results. OBJECTIVES: A comparable data structure in the different screening centers, with uniform definitions of primary parameters is essential for the nationwide evaluation of UNHS results. To address the question of whether a data structure with comparable definitions already exists or still has to be created, the existing structures and primary parameter definitions in the hearing screening centers should be investigated and compared. METHODS: A survey was conducted in all hearing screening centers to assess how data on the primary UNHS parameters defined in pediatric guidelines was gathered. In the case of discrepancies, uniform definitions were created. Finally, the practicability of these definitions was evaluated. RESULTS: Due to differing definitions of primary parameters, some of the data were not comparable between the individual centers. Therefore, uniform definitions were created in a consensus process. In the centers, the screening method, the two-step first screening and the result of the first screening now correspond to these uniform definitions. Other parameters, e.g. the total number of newborns, still vary widely, rendering the comparison of screening rates almost impossible. CONCLUSION: Valid evaluation of UNHS not only requires nationwide establishment of hearing screening centers, but also unified data structures and parameter definitions.

[Dysphagia]. / Dysphagie.

Difficulties in swallowing occur in every age and have a great impact on the morbidity as well as on the mortality in patients especially if also an aspiration occurs. This article reports on the one hand the anatomy and physiology in the normal process of swallowing. On the other hand the cause of dysphagia, the diagnostic possibilities and therapeutic approaches are described.

Development of auditory localization accuracy and auditory spatial discrimination in children and adolescents.

The present study investigated the development of two parameters of spatial acoustic perception in children and adolescents with normal hearing, aged 6-18 years. Auditory localization accuracy was quantified by means of a sound source identification task and auditory spatial discrimination acuity by measuring minimum audible angles (MAA). Both low- and high-frequency noise bursts were employed in the tests, thereby separately addressing auditory processing based on interaural time and intensity differences. Setup consisted of 47 loudspeakers mounted in the frontal azimuthal hemifield, ranging from 90° left to 90° right (-90°, +90°). Target signals were presented from 8 loudspeaker positions in the left and right hemifields (±4°, ±30°, ±60° and ±90°). Localization accuracy and spatial discrimination acuity showed different developmental courses. Localization accuracy remained stable from the age of 6 onwards. In contrast, MAA thresholds and interindividual variability of spatial discrimination decreased significantly with increasing age. Across all age groups, localization was most accurate and MAA thresholds were lower for frontal than for lateral sound sources, and for low-frequency compared to high-frequency noise bursts. The study also shows better performance in spatial hearing based on interaural time differences rather than on intensity differences throughout development. These findings confirm that specific aspects of central auditory processing show continuous development during childhood up to adolescence.

Growth mechanism and properties of InGaN insertions in GaN nanowires.

We demonstrate the strong influence of strain on the morphology and In content of InGaN insertions in GaN nanowires, in agreement with theoretical predictions which establish that InGaN island nucleation on GaN nanowires may be energetically favorable, depending on In content and nanowire diameter. EDX analyses reveal In inhomogeneities between the successive dots but also along the growth direction within each dot, which is attributed to compositional pulling. Nanometer-resolved cathodoluminescence on single nanowires allowed us to probe the luminescence of single dots, revealing enhanced luminescence from the high In content top part with respect to the lower In content dot base.

[Dysphonia in children and adolescents]. / Stimmstörungen bei Kindern und Jugendlichen.

Hoarseness is the leading symptom of dysphonia among children and adolescents. The incidence is evaluated internationally to be 6-25%. In an overview the hereditary and acquired organic and functional causes including secondary organic lesions of the vocal folds, the pathomechanisms and the symptoms typical for this age group are presented. In clinical routine, symptoms of dysphonia in children and adolescents should be consciously looked for and any long-term hoarseness should be examined by specialized physicians, even in this age group, using methods suitable to the age group and the developmental stage. When the appropriate indications are present all therapeutic options currently available should be taken into consideration. Furthermore, this paper provides information for the parents concerning the imminent phoniatric examination.

Complementary cathodoluminescence lifetime imaging configurations in a scanning electron microscope.

Cathodoluminescence (CL) spectroscopy provides a powerful way to characterize optical properties of materials with deep-subwavelength spatial resolution. While CL imaging to obtain optical spectra is a well-developed technology, imaging CL lifetimes with nanoscale resolution has only been explored in a few studies. In this paper we compare three different time-resolved CL techniques and compare their characteristics. Two configurations are based on the acquisition of CL decay traces using a pulsed electron beam that is generated either with an ultra-fast beam blanker, which is placed in the electron column, or by photoemission from a laser-driven electron cathode. The third configuration uses measurements of the autocorrelation function g(2) of the CL signal using either a continuous or a pulsed electron beam. The three techniques are compared in terms of complexity of implementation, spatial and temporal resolution, and measurement accuracy as a function of electron dose. A single sample of InGaN/GaN quantum wells is investigated to enable a direct comparison of lifetime measurement characteristics of the three techniques. The g(2)-based method provides decay measurements at the best spatial resolution, as it leaves the electron column configuration unaffected. The pulsed-beam methods provide better detail on the temporal excitation and decay dynamics. The ultra-fast blanker configuration delivers electron pulses as short as 30 ps at 5 keV and 250 ps at 30 keV. The repetition rate can be chosen arbitrarily up to 80 MHz and requires a conjugate plane geometry in the electron column that reduces the spatial resolution in our microscope. The photoemission configuration, pumped with 250 fs 257 nm pulses at a repetition rate from 10 kHz to 25 MHz, allows creation of electron pulses down to a few ps, with some loss in spatial resolution.

[Large endolymphatic duct and sac syndrome : part 2: clinical manifestations]. / Der erweiterte Ductus und Saccus endolymphaticus : Teil 2: Klinische Manifestationen.

OBJECTIVE: The aim of this study was to clarify the clinical course of large endolymphatic duct and sac syndrome (LEDS). Although LEDS is the most common form of radiologically detectable inner ear malformation associated with sensorineural hearing loss (SNHL), it is relatively unknown in the German-speaking countries. We hoped to derive useful pointers for clinical care. METHODS: We evaluated the clinical audiometric records and imaging findings of 169 patients with clinically suspected inner ear malformation seen between 1994 and 2003. Following identification of all LEDS cases, we serially investigated the anamnestic and functional data with regard to severity and course. RESULTS: Among 169 patients, 17 (median age 12 years; 12 females) showed LEDS. A total of 28 ears were affected. Clinically, most cases were of prelingual or perilingual onset and displayed steady or fluctuatingly progressive severe SNHL with emphasis on the high frequencies or deafness. Episodes of sudden hearing loss were relatively frequent. No correlation could be demonstrated between the severity of morphological changes and the degree of SNHL. CONCLUSION: Progression of SNHL and episodes of sudden hearing loss were seen mainly in late childhood or adolescence. This should be taken into account when informing and advising patients and planning therapy.