Waveguide-coupled nanopillar metal-cavity light-emitting diodes on silicon.

Nanoscale light sources using metal cavities have been proposed to enable high integration density, efficient operation at low energy per bit and ultra-fast modulation, which would make them attractive for future low-power optical interconnects. For this application, such devices are required to be efficient, waveguide-coupled and integrated on a silicon substrate. We demonstrate a metal-cavity light-emitting diode coupled to a waveguide on silicon. The cavity consists of a metal-coated III-V semiconductor nanopillar which funnels a large fraction of spontaneous emission into the fundamental mode of an InP waveguide bonded to a silicon wafer showing full compatibility with membrane-on-Si photonic integration platforms. The device was characterized through a grating coupler and shows on-chip external quantum efficiency in the 10-4-10-2 range at tens of microamp current injection levels, which greatly exceeds the performance of any waveguide-coupled nanoscale light source integrated on silicon in this current range. Furthermore, direct modulation experiments reveal sub-nanosecond electro-optical response with the potential for multi gigabit per second modulation speeds.

Highly efficient metal grating coupler for membrane-based integrated photonics.

We present the design of a metal grating coupler compatible with membrane photonic circuit platforms, consisting of a buried metal grating and a metal mirror. A nonapodized design provides a fiber-to-chip coupling efficiency at 1.55 µm up to 73%, whereas apodized designs show theoretical efficiencies as high as 89%, with a 3 dB bandwidth of 61 and 78 nm, respectively. An important advantage is that the coupling efficiency is independent from the underlying layer stack, enabling its use in diverse applications. For example, a thin buffer layer is required to achieve optical coupling for the heterogeneous integration of III-V and silicon photonics, whereas a thick buffer is of interest for thermal isolation between photonic membranes and CMOS circuits.

Piezoelectric control of the mobility of a domain wall driven by adiabatic and non-adiabatic torques.

The rich internal degrees of freedom of magnetic domain walls make them an attractive complement to electron charge for exploring new concepts of storage, transport and processing of information. Here we use the tunable internal structure of a domain wall in a perpendicularly magnetized GaMnAsP/GaAs ferromagnetic semiconductor and demonstrate devices in which piezoelectrically controlled magnetic anisotropy yields up to 500% mobility variations for an electrical-current-driven domain wall. We observe current-induced domain wall motion over a wide range of current-pulse amplitudes and report a direct observation and the piezoelectric control of the Walker breakdown separating two regimes with different mobilities. Our work demonstrates that in spin-orbit-coupled ferromagnets with weak extrinsic domain wall pinning, the piezoelectric control allows one to experimentally assess the upper and lower boundaries of the characteristic ratio of adiabatic and non-adiabatic spin-transfer torques in the current-driven domain wall motion.

Coplanar stripline antenna design for optically detected magnetic resonance on semiconductor quantum dots.

We report on the development and testing of a coplanar stripline antenna that is designed for integration in a magneto-photoluminescence experiment to allow coherent control of individual electron spins confined in single self-assembled semiconductor quantum dots. We discuss the design criteria for such a structure which is multi-functional in the sense that it serves not only as microwave delivery but also as electrical top gate and shadow mask for the single quantum dot spectroscopy. We present test measurements on hydrogenated amorphous silicon, demonstrating electrically detected magnetic resonance using the in-plane component of the oscillating magnetic field created by the coplanar stripline antenna necessary due to the particular geometry of the quantum dot spectroscopy. From reference measurements using a commercial electron spin resonance setup in combination with finite element calculations simulating the field distribution in the structure, we obtain a magnetic field of 0.12 mT at the position where the quantum dots would be integrated into the device. The corresponding π-pulse time of ≈0.5 µs meets the requirements set by the high sensitivity optical spin read-out scheme developed for the quantum dot.

Comparison of dynamic MR imaging of the breast and sestamibi scintimammography for evaluation of indeterminate mammographic lesions.

The aim of this study was to compare Tc-99m sestamibi scintimammography and dynamic contrast-enhanced MR imaging for the evaluation of indeterminate mammographic lesions. Forty patients with questionable mammographic findings were included in a prospective study. Thirty lesions were non-palpable. Mean lesion size was 1.6+/-0.7 cm (range 0.5-3.5 cm). Scintigraphy was considered as malignant when focal tracer accumulation was present. In MR imaging, lesions were classified according to their signal intensity time course: no enhancement or steady enhancement with low signal intensity (M0); steady enhancement with high signal intensity (M1); or rapid enhancement with plateau (M2) or washout (M3). Lesions classified as M2 or M3 were considered as suspicious for malignancy. Histopathologic evaluation was performed in 24 lesions. In 16 cases lesions were classified as benign from follow-up examinations (mean 24 months). Malignancies were proven in 14 patients (9 invasive carcinomas, 5 ductal carcinoma in situ). Sensitivity of MR imaging was 12 of 14 (86%) and sensitivity of scintimammography was 8 of 14 (57%). One of 26 benign lesions was false positive at MR imaging. Scintigraphy showed no false-positive results. In conclusion, magnetic resonance imaging provided high accuracy in evaluation of indeterminate mammographic lesions. Sensitivity of scintimammography was too low in detecting small carcinomas.

Muscular contractions and their effect on the vertical ground reaction force during quiet stance--Part I: Hypothesis and experimental investigation.

There is no consensus as to the origins of the oscillations of the vertical ground reaction force during quiet stance. The concept of a cardiovascular origin is supported by many ballistocardiographic studies, but its exclusivity has never been proven. A new hypothesis was formulated to explain their genesis: there is a neuromuscular postural control system, possibly different from the well-investigated mechanisms controlling the macroscopic sway, responsible for compensating the small endogenous forces perturbing the posture by causing some muscles to contract proportionately to the magnitude of perturbation. These contractions contribute to the ground reaction force oscillations. To verify this hypothesis, a series of experiments simultaneously recording the electrocardiogram, the electromyogram of several muscles, and the ground reaction forces were conducted on ten informed and consenting human subjects. The experimental results confirmed that the hypothesized muscular activity in response to the perturbation induced by the cardiac contraction and subsequent blood movement does in fact exist. The signal detected by electromyography is not a cardioelectric artifact, but an actual myoelectrical activity. Several interesting patterns of muscular activity emerged in this investigation. These results provide the needed background and justification for investigating the use of the vertical ground reaction force, not only in the study of posture, but also in the study of clinical conditions affecting the neuromuscular control and the musculature of the trunk.

Muscular contractions and their effect on the vertical ground reaction force during quiet stance--Part II: Mathematical model.

A one-dimensional lumped-parameters mathematical model of the standing human was developed to specifically investigate how the muscular activity and the cardiovascular forces originated by the heart movement and the blood ejection in the ascending aorta affect the ground reaction force in the head-to-toes direction. The forces produced by the cardiovascular activity were modeled by a time-varying force actuator connected to the torso whose characteristics were obtained from the literature. The muscles identified as active during Part I of this work, mainly the erector spinae and oblique abdominal muscles, were modeled as a single force actuator acting with equal and opposite force between the pelvis and the thoracic spine. The force versus time data were obtained from the electromyographic signals obtained in Part I. Although the model of the human body used in this investigation was simple, the results of the simulations clearly showed that the cardiovascular forces alone are not sufficient for generating the large negative (i.e., upward) peak observed in the vertical ground reaction force. The peaks were mainly the result of a very modest muscular contraction of the spinal muscles. The simulations offer further evidence to support the hypothesis that trunk muscles contractions are capable of generating vertical ground reaction force oscillations that are consistent with the experimental results. These oscillations are apparently generated by a combination of cardiovascular and muscular forces.

Anticipatory control of vertical lifting force and momentum during the squat lift with expected and unexpected loads.

STUDY DESIGN: Mixed, repeated measures design. OBJECTIVES: To determine if previous experience with loads of similar weight influences the anticipatory lifting force and postural adjustments during the squat lift. To examine a multijoint, functional task for coordination between stability and movement. To determine if lifting unexpected loads results in trunk loading patterns associated with greater injury risk. BACKGROUND: Workers are increasingly exposed to variability in materials handling thereby increasing the risk of injury. Understanding the control processes underlying lifting will support clinical decision making for preparing injured workers to return to realistic working conditions. METHODS AND MEASURES: Subjects (19 men, 4 women; mean age, 25.4 +/- 3.5 y) lifted a series of boxes weighing 5%, 20%, and 35% of their maximal lifting capacity. The loads were delivered via a gravity conveyor. The identical-appearing loads were ordered so that the subjects lifted several loads of similar weight, immediately followed by a lighter or heavier than expected load based on the previous lift. RESULTS: Generally, the vertical lifting force, force rate, horizontal momentum, and angular momentum increased with an increase in expected load. Higher peak lumbar extensor moments occurred with lighter than expected loads (expected 20% and lifted 5% load = 238.2 +/- 91.2 N-m; expected 35% and lifted 5% load = 278.2 +/- 101.8 N-m) compared to expected loads of similar weight (expected and lifted 5% load = 205.0 +/- 73.2 N-m). Heavier than expected loads led to eccentric trunk movements when there were large mismatches between the expected and actual loads. CONCLUSIONS: The vertical lifting forces and whole body momentum were predictively scaled according to the expected load. The loading phase relationships indicated coordination between the lifting force, force rate, horizontal momentum, and angular momentum. Trunk loading during the lifts with unexpected loads showed patterns associated with increased injury risk.

[A combined PACS and Internet information system in a university medical center]. / Kombiniertes PACS und Intranet-Informationssystem an einem Universitätsklinikum.

PURPOSE: The Department of Radiology at the University Hospital Innenstadt Munich provides all clinical departments of a large university hospital with several radiology units at different locations. During the last four years all units have been fully digitalized with a stepwise installation of a PACS. The PACS also processes images from the Nuclear Medicine Department. METHODS: As image modalities, archive systems and review workstations, we use devices from multiple vendors, which are integrated into a consistent system using the DICOM standard. The hospital has developed its own RIS and an Internet information system, which provides access to all reports and images from radiology for all clinical departments inside the hospital. Additionally, other clinical information such as laboratory results or ECG examinations are available through the system. RESULTS: After one year of operation, the system succeeded in the clinical routine work as the primary source for radiological reports and images as well as for laboratory values. CONCLUSION: The advantages of digitalization were, besides reduction of film cost, especially optimizations of work flow with access to digital images from everywhere at any time.

Adhesio interthalamica in male patients with schizophrenia.

OBJECTIVE: The authors investigated whether absence of the adhesio interthalamica in patients with schizophrenia constitutes a marker of early developmental neuropathological changes. METHOD: Thirty male patients with schizophrenia and 30 healthy male subjects were recruited for study. Magnetic resonance imaging was performed, and the presence or absence of the adhesio interthalamica was determined for each subject. The length and volume of the third ventricle were also measured. RESULTS: No differences in the presence or absence of the adhesio interthalamica were found between patients with schizophrenia and normal comparison subjects. Patients without the adhesio interthalamica had significantly higher scores for negative symptoms than patients with the adhesio interthalamica. There was no correlation between absence of the adhesio interthalamica and length and volume of the third ventricle in either patients or comparison subjects. CONCLUSIONS: The findings suggest that patients with schizophrenia who do not have the adhesio interthalamica are characterized by more severe negative symptoms.

Normative volumetric data of the developing hippocampus in children based on magnetic resonance imaging.

PURPOSE: To acquire normative data of the hippocampus and its postnatal growth in 50 children (age, 1 month to 15 years) without epilepsy. METHODS: Morphometry of the hippocampus was carried out by using a spoiled FLASH 3D sequence (sagittal orientation), whereas the volume of the brain was assessed with a T2-weighted spin-echo sequence (transverse orientation). The volume of the hippocampus and the brain was determined by following Cavalieri's principle. Growth curves of the brain and hippocampus were fitted to a nonlinear Boltzmann sigmoidal equation. RESULTS: Intra-/interobserver coefficient of variation was 2.0/4.9% for hippocampal volume measurements and 2.0/2.1% for brain volumetry. A significant difference in volume was noted between the right and left hippocampus (p < 0.001), with the right side being larger on average by 0.10 cc. Correlation coefficients of growth curves ranged between 0.71 and 0.94. Growth curves demonstrated a faster development of the hippocampus in girls. A steeper slope of hippocampal growth as compared with brain growth was found in girls, whereas in boys, the slope of brain growth was steeper. CONCLUSIONS: Our findings will be of help in evaluating vulnerable phases of the hippocampal formation with accelerated growth, thereby leading to a better understanding of the development of hippocampal sclerosis in early childhood.

Corpus callosum size in schizophrenia--a magnetic resonance imaging analysis.

Previous MRI studies have shown differences in corpus callosum size between schizophrenic patients and controls. The corpus callosum (CC), as the main interhemispheric fiber tract, plays an important role in interhemispheric integration and communication. Though MRI studies suggest smaller CC in schizophrenia, there are still conflicting findings. Using in vivo magnetic resonance imaging, it was investigated whether the midsagittal area of CC differs between twenty-three right-handed male schizophrenic patients and twenty-three matched controls. Total CC area, five subregions of CC, total brain volume, gray and white matter were measured. No differences between schizophrenic patients and controls were found regarding all CC measurements, total brain volume, and gray matter tissue. However, a significant reduction of white matter tissue in the patient group emerged. There was no correlation between CC morphology and clinical variables such as age of onset, length of illness or symptom severity. Interestingly, five schizophrenic patients with a positive family history of schizophrenia showed significant reduction of the subregion C3, associated with a reduced total brain and gray and white matter volume. Significant reduction in the CC and its subregions was not confirmed in this group of patients with schizophrenia. In the subgroup of schizophrenic patients with a positive family history of schizophrenia, a significant reduction of the subregion corresponding to a part of the trunk of the CC was found.

An electromyographic comparison of abdominal muscle synergies during curl and double straight leg lowering exercises with control of the pelvic position.

STUDY DESIGN: This prospective study evaluated the abdominal muscle activity during the Isometric bent knee curl and double straight leg lowering exercise. OBJECTIVES: To compare the magnitude of the electromyographic activity across the curl and double straight leg lowering exercise and determine if the muscle synergies were specific to a given exercise. SUMMARY OF BACKGROUND DATA: Abdominal muscle strengthening exercises are frequently recommended in the prevention and rehabilitation of individuals with low back pain. Previous studies comparing the curl exercise with the double straight leg lowering exercise did not support the notion that the double straight leg lowering exercise is more demanding on the abdominal muscles. No previous study examined these two exercises while maintaining a constant pelvic position. METHODS: Fifteen male subjects had the electromyographic activity of the rectus abdominis, the external oblique, and the internal oblique abdominal muscles evaluated during the curl and double straight leg lowering exercise. The same position of the posterior pelvic tilt was maintained between each exercise using feedback from an electrogoniometer attached to the pelvis. RESULTS: The double straight leg lowering exercise resulted in significantly greater activation of the abdominal muscles compared with the curl. Two abdominal muscle synergies emerged during the double straight leg lowering exercise: synergy I exhibited high rectus abdominis, high external oblique, and low internal oblique muscle activity, whereas synergy II exhibited low rectus abdominis, high external oblique, and high internal oblique. CONCLUSIONS: The results support the use of the double straight leg lowering with the posterior pelvic tilt for achieving greater abdominal muscle coactivation in an exercise program.

Persistent mirror movements: functional MR imaging of the hand motor cortex.

PURPOSE: To compare cortical areas involved in hand motor function in patients with persistent motor movements with those in healthy control subjects by using functional magnetic resonance (MR) imaging. MATERIALS AND METHODS: Nine patients (five patients with autosomal-dominant mirror movements, three with Kallmann syndrome, one with Wildervanck syndrome) and 10 healthy control subjects participated in the study. Functional MR imaging was performed at 1.5 T with a two-dimensional fast low-angle shot sequence. Participants were imaged while performing sequential finger-thumb opposition and during a rest period. RESULTS: During unimanual intentional movements, MR imaging in all control subjects showed increased signal intensity along the superior bend of the central sulcus contralateral to the moved hand. This increase was predominantly located in a region that included the medial part of the precentral gyrus. In contrast, MR imaging in patients with mirror movements showed bilateral activity in the medial region of the precentral gyrus. CONCLUSION: Bifurcations of the corticospinal tract may not be solely responsible for mirror movements. Bilateral activity of the primary motor cortex seems to play an additional role.

Interinnominate motion and symmetry: comparison between gymnasts and nongymnasts.

Some clinical approaches to the treatment of low back pain evaluate and treat observed asymmetries of pelvic posture and motion. Scientific evidence suggests the motion available between the innominate bones is small and variable in nature. The purposes of this investigation were 1) to determine if interinnominate motion of subjects without low back pain was symmetrical in reciprocal test posture combinations, 2) to assess innominate bone symmetry in standing, and 3) to determine if a difference in the magnitude of interinnominate motion was present between a subject group which performs more frequent flexibility activities compared with a subject group representing the general population. Thirty-four subjects (eight male gymnasts, nine female gymnasts, eight male nongymnasts, and nine female nongymnasts) were evaluated in standing and three other reciprocal postures (modified standing, modified sitting, and half-kneeling). In each posture, the Metrecom Skeletal Analysis System was used to obtain coordinates for the anterior and posterior iliac spines. Projection angles were used to determine the relative positions of the right and left innominate bones. Results suggest that stand to right modified standing and stand to left modified standing oblique sagittal interinnominate composite motions were symmetrical, stand to right modified sitting and stand to left modified sitting oblique sagittal interinnominate composite motions were asymmetrical, and stand to right half-kneel and stand to left half-kneel oblique sagittal interinnominate composite motions' symmetrical properties were mixed depending on the group. Gymnasts as a group were found to have asymmetrically positioned innominate bones while nongymnasts as a group had symmetrically positioned innominate bones.

[The motor hand area. Noninvasive detection with functional MRI and surgical validation with cortical stimulation]. / Das motorische Handareal. Nichtinvasiver Nachweis mittels fMRT und operative Validierung mit kortikaler Stimulation.

In this study, activation of cortical sites by specific motor tasks (opening and closing of the hand) was examined by fMRI utilizing the blood-oxygen-level-dependent (BOLD) technique. fMRI was employed in five volunteers and in six patients with tumors in the vicinity of the central region. In the patients, the fMRI data and intraoperative cortical mapping were compared. Our results indicate good correlation of these two methods and that there are no significant differences in the localization of the motor hand area.

Geriatric care management reduces Medicare losses.

Healthcare costs for the elderly are rising rapidly in the United States. One way for a hospital to control these rising costs is to implement a geriatric care management system. The goal of a such a system is to change the way the hospital treats medically complex Medicare patients and, thus, reduce unnecessary hospital costs. Such a system requires a process for identifying elderly patients in need of geriatric care management services, treating them efficiently, and assessing the system itself. An effective process usually results in significant cost savings for the hospital as well as improved patient care and satisfaction.

In vivo acetabular contact pressures during rehabilitation, Part I: Acute phase.

The authors conducted a two-part study to compare in vivo acetabular contact pressures during the acute and postacute phases of rehabilitation. This report compares in vivo acetabular contact pressures generated during selected "inpatient" rehabilitation activities and their relationship to pain, range of motion, and other clinical indicators. A pressure-instrumented Moore-type endoprosthesis was implanted in a 73-year-old woman who had sustained a femoral neck fracture. Acetabular contact pressures during the first 2 weeks after surgery were rank-ordered. Clinical data, including range of motion, manual muscle test grade, use of pain medication, and independence in gait, were collected simultaneously. Acetabular pressures did not follow the predicted rank order corresponding to the commonly prescribed temporal order of inpatient rehabilitation activities. Isometric hip extension and active hip flexion generated the highest pressures of all the studied activities, including those measured during gait activities. Isometric exercises, therefore, may not be entirely benign preparation for ambulatory activity. Clinical data did not correspond with peak pressure data, suggesting that observed responses to rehabilitation may not be dependable criteria for progressing the acute hip rehabilitation protocol. We discuss applications for rehabilitation programs based on hip contact pressure data as an initial attempt to formulate more defensible rehabilitation approaches for patients with acutely painful hips.

In vivo acetabular contact pressures during rehabilitation, Part II: Postacute phase.

The authors conducted a two-part study to compare in vivo acetabular contact pressures during the acute and postacute phases of rehabilitation in a single subject with a pressure-instrumented femoral prosthesis. This report compares six common hip rehabilitation activities for resultant in vivo hip pressure magnitudes during the first 5 years after discharge from an acute care hospital. These activities were full, partial, touch-down, and non-weight-bearing ambulation and isometric hip abduction and straight-leg-raising exercises. A pressure-instrumented femoral endoprosthesis implanted in a 73-year-old woman who had sustained a femoral neck fracture provided data for the activities. The activities were rank ordered and compared over time according to peak pressure magnitude. Prescribed weight bearing and exercise type were not good predictors of hip peak pressures in this patient. Maximum pressures occurred by 1 year postdischarge for most activities, with a tendency to stabilize or decline thereafter. Resisted isometric hip abduction exercise demonstrated the most variation over time. The results suggest that hip pressures may be limited by controlling muscle force and movement velocity during postoperative hip rehabilitation activities.