High-responsivity graphene photodetectors integrated on silicon microring resonators

Graphene integrated photonics provides several advantages over conventional Si photonics. Single layer graphene (SLG) enables fast, broadband, and energy-efficient electro-optic modulators, optical switches and photodetectors (GPDs), and is compatible with any optical waveguide. The last major barrier to SLG-based optical receivers lies in the current GPDs' low responsivity when compared to conventional PDs. Here we overcome this by integrating a photo-thermoelectric GPD with a Si microring resonator. Under critical coupling, we achieve >90% light absorption in a ~6 μm SLG channel along a Si waveguide. Cavity-enhanced light-matter interactions cause carriers in SLG to reach ~400 K for an input power ~0.6 mW, resulting in a voltage responsivity ~90 V/W, with a receiver sensitivity enabling our GPDs to operate at a 10-9 bit-error rate, on par with mature semiconductor technology, but with a natural generation of a voltage, rather than a current, thus removing the need for transimpedance amplification, with a reduction of energy-per-bit, cost, and foot-print.

Prenatal muscle forces are necessary for vertebral segmentation and disc structure, but not for notochord involution in mice

Embryonic muscle forces are necessary for normal vertebral development and spinal curvature, but their involvement in intervertebral disc (IVD) development remains unclear. The aim of the current study was to determine how muscle contractions affect (1) notochord involution and vertebral segmentation, and (2) IVD development including the mechanical properties and morphology, as well as collagen fibre alignment in the annulus fibrosus. Muscular dysgenesis (mdg) mice were harvested at three prenatal stages: at Theiler Stage (TS)22 when notochord involution starts, at TS24 when involution is complete, and at TS27 when the IVD is formed. Vertebral and IVD development were characterised using histology, immunofluorescence, and indentation testing. The results revealed that notochord involution and vertebral segmentation occurred independently of muscle contractions between TS22 and TS24. However, in the absence of muscle contractions, we found vertebral fusion in the cervical region at TS27, along with (i) a displacement of the nucleus pulposus towards the dorsal side, (ii) a disruption of the structural arrangement of collagen in the annulus fibrosus, and (iii) an increase in viscous behaviour of the annulus fibrosus. These findings emphasise the important role of mechanical forces during IVD development, and demonstrate a critical role of muscle loading during development to enable proper annulus fibrosus formation. They further suggest a need for mechanical loading in the creation of fibre-reinforced tissue engineering replacement IVDs as a therapy for IVD degeneration.

236Automatic classification of 20 different types of atrial tachycardia using 12-lead ECG signals

Funding Acknowledgements

Supported by the European Union"s Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreement No.766082 (MY-ATRIA)

Background

 Atrial Flutter (AFl) as a common reentrant atrial tachycardia is driven by self-sustainable mechanisms that cause excitation to propagate along pathways different from sinus rhythm. Intracardiac electrophysiological mapping and catheter ablation is often performed without prior knowledge of the mechanism perpetuating AFl in a given patient, likely prolonging the procedure time of these invasive interventions. We investigated the feasibility of automatically identifying 20 different AFl types based on the non-invasive 12-lead electrocardiogram (ECG) using machine learning. 

Methods

 Electrophysiological fast marching computer simulations of 20 different atrial tachycardia scenarios (micro-/macro-reentry, scar-related/anatomical/functional, figure-of-eight, focal, different locations) were performed and propagated to the standard 12-lead ECG based on the Courtemanche atrial action potential model. The virtual study population comprised combinations of 8 different anatomical bi-atrial models with 2 orientational variants each and 8 different torso models yielding a total of 2512 ECGs. From each ECG, we extracted 114 features from different domains (e.g., time, frequency, entropy, wavelet, non-linear recurrence analysis). The dataset was randomly split into 1256 training samples, 628 validation samples and 628 test samples while maintaining a balanced AFl type distribution. A radial basis neural network (RBNN) was trained as a classifier after selection of the most informative features. 

Results

The RBNN yielded a test set accuracy of 90% regarding the identification of the AFl mechanism using 10 features (from different domains). The most discriminative single feature was the cycle length that alone led to a test set accuracy of 74%, while the remaining feature set without cycle length (9 features) reduced the test set accuracy to 33%. The machine learning approach generalized well regarding unseen torso geometries (90% accuracy if training was performed on only 7 torso models) but rather poor regarding atrial anatomies (23% if the atrial anatomical model was not seen during training) indicating that more than the currently used 8 atrial models should be included during training to cover the relevant anatomical variability. 

Conclusions

Our results show that a machine learning classifier can potentially identify a high number of different AFl types using the 12-lead ECG. This non-invasive method can aid in planning and tailoring AFl treatment for patients. Application to clinical data is necessary as a next step to pave the way for clinical translation.

Abstract Figure.

Evaluation of the inflammatory markers CCL8, CXCL5, and LIF in patients with anastomotic leakage after colorectal cancer surgery

PURPOSE

Anastomotic leakage constitutes a dreaded complication after colorectal surgery, leading to increased morbidity and mortality as well as prolonged hospitalization. Most leakages become clinically apparent about 8 days after surgery; however, early detection is quintessential to reduce complications and to improve patients' outcome. We therefore investigated the significance of specific protein expression profiles as putative biomarkers, indicating anastomotic leakage.

METHODS

In this single-center prospective cohort study serum and peritoneal fluid samples-from routinely intraoperatively inserted drainages-of colorectal cancer patients were collected 3 days after colorectal resection. Twenty patients without anastomotic leakage and 18 patients with an anastomotic leakage and without other complications were included. Protein expression of seven inflammatory markers in serum and peritoneal fluid was assessed by multiplex ELISA and correlated with patients' clinical data.

RESULTS

Monocyte chemoattractant protein 2 (CCL8/MCP-2), leukemia-inhibiting factor (LIF), and epithelial-derived neutrophil-activating protein (CXCL5/ENA-78) were significantly elevated in peritoneal fluid but not in serum samples from patients subsequently developing anastomotic leakage after colorectal surgery. No expressional differences could be found between grade B and grade C anastomotic leakages.

CONCLUSION

Measurement 3 days after surgery revealed altered protein expression patterns of the inflammatory markers CCL8/MCP2, LIF, and CXCL5/ENA-78 in peritoneal fluid from patients developing anastomotic leakage after colorectal surgery. Further studies with a larger patient cohort with inclusion of different variables are needed to evaluate their potential as predictive biomarkers for anastomotic leakage.

Rituximab and bilateral HSV epithelial keratitis in a patient with mucous membrane pemphigoid

Background

B cell depleting therapy is widely used for lymphoproliferative diseases and immune-mediated disorders, including mucous membrane pemphigoid. The latter is an autoimmune blistering disease affecting predominantly the mucosae potentially associated with devastating complications.

Methods

A 71-year-old patient with severe mucous membrane pemphigoid involving ocular, oral pharyngeal and laryngeal involvement is described. To control the disease, the patient was given rituximab therapy in combination with oral corticosteroids. He subsequently experienced an epithelial herpes simplex virus keratitis in one eye and 3 months later in his fellow eye. Topical treatment with ganciclovir resulted in prompt recovery.

Results

For the first time, a correlation between rituximab and bilateral epithelial herpes simplex virus keratitis is described.

Conclusions

Although rituximab is a promising biologic agent for the treatment of autoimmune diseases, it bears the risk of reactivation of viral infections, including the onset of herpes simplex virus keratitis.

4.3 μm quantum cascade detector in pixel configuration

We present the design simulation and characterization of a quantum cascade detector operating at 4.3μm wavelength. Array integration and packaging processes were investigated. The device operates in the 4.3μm CO₂ absorption region and consists of 64 pixels. The detector is designed fully compatible to standard processing and material growth methods for scalability to large pixel counts. The detector design is optimized for a high device resistance at elevated temperatures. A QCD simulation model was enhanced for resistance and responsivity optimization. The substrate illuminated pixels utilize a two dimensional Au diffraction grating to couple the light to the active region. A single pixel responsivity of 16mA/W at room temperature with a specific detectivity D^* of 5⋅10⁷ cmHz/W was measured.

Three-dimensional spheroids of adipose-derived mesenchymal stem cells are potent initiators of blood vessel formation in porous polyurethane scaffolds

Adipose-derived mesenchymal stem cells (adMSCs) exhibit a high angiogenic activity. Accordingly, their incorporation into tissue constructs represents a promising vascularization strategy in tissue engineering. In the present study, we analyzed whether the efficacy of this approach can be improved by seeding adMSCs as three-dimensional spheroids onto porous scaffolds. Green fluorescent protein (GFP)-positive adMSCs expressing CD13, CD73, CD90 and CD117 were isolated from C57BL/6-TgN(ACTB-EGFP)1Osb/J mice for the generation of spheroids using the liquid overlay technique. Porous polyurethane scaffolds were seeded with these spheroids or a comparable number of individual adMSCs and implanted into the dorsal skinfold chamber of C57BL/6 wild-type mice. The vascularization of the implants was analyzed and compared to non-seeded scaffolds by means of intravital fluorescence microscopy and immunohistochemistry. The adMSC spheroids exhibited a homogeneous diameter of ~270μm and could easily be incorporated into the scaffolds by dynamic seeding. After implantation, they induced a strong angiogenic host tissue response, resulting in an improved scaffold vascularization with a significantly higher functional microvessel density when compared to non-seeded scaffolds and scaffolds seeded with individual adMSCs. Immunohistochemical analyses revealed that a high fraction of ~40% of all microvessels within the center of spheroid-seeded scaffolds developed from GFP-positive adMSCs. These vessels inosculated with ingrowing GFP-negative vessels of the host. This indicates that adMSC spheroids serve as individual vascularization units, promoting the simultaneous development of new microvascular networks at different locations inside implanted tissue constructs. Thus, adMSC spheroids may be used to increase the efficacy of MSC-based vascularization strategies in future tissue engineering applications.

Vascularisation of porous scaffolds is improved by incorporation of adipose tissue-derived microvascular fragments

In tissue engineering, the generation of tissue constructs comprising preformed microvessels is a promising strategy to guarantee their adequate vascularisation after implantation. Herein, we analysed whether this may be achieved by seeding porous scaffolds with adipose tissue-derived microvascular fragments. Green fluorescent protein (GFP)-positive microvascular fragments were isolated by enzymatic digestion from epididymal fat pads of male C57BL/6-TgN(ACTB-EGFP)1Osb/J mice. Nano-size hydroxyapatite particles/poly(ester-urethane) scaffolds were seeded with these fragments and implanted into the dorsal skinfold chamber of C57BL/6 wild-type mice to study inosculation and vascularisation of the implants by means of intravital fluorescence microscopy, histology and immunohistochemistry over 2 weeks. Empty scaffolds served as controls. Vital microvascular fragments could be isolated from adipose tissue and seeded onto the scaffolds under dynamic pressure conditions. In the dorsal skinfold chamber, the fragments survived and exhibited a high angiogenic activity, resulting in the formation of GFP-positive microvascular networks within the implants. These networks developed interconnections to the host microvasculature, resulting in a significantly increased functional microvessel density at day 10 and 14 after implantation when compared to controls. Immunohistochemical analyses of vessel-seeded scaffolds revealed that >90 % of the microvessels in the implants' centre and ~60 % of microvessels in the surrounding host tissue were GFP-positive. This indicates that the scaffolds primarily vascularised by external inosculation. These novel findings demonstrate that the vascularisation of implanted porous scaffolds can be improved by incorporation of microvascular fragments. Accordingly, this approach may markedly contribute to the success of future tissue engineering applications in clinical practice.

Solar Cells Based on PVD Grown CuGaSe2 – Absorber and Device Properties

For solar cells based on CuGaSe2(CGS) absorber layers physical vapour deposition (PVD) was employed to deposit polycrystalline CGS thin films. Efficiencies up to 7.9% were achieved by applying a two-stage deposition process for absorber preparation. The high structural quality of the absorbers is shown. For highest cell efficiencies our standard recipe for the CdS buffer deposition had to be re-adapted. Voltage dependent spectral response measurements of the device in conjunction with absorption measurements of the absorber layers allow calculation of the minority carrier diffusion length, space charge region (SCR) width, absorber carrier concentration and the built-in voltage. The defect state density at the buffer/absorber interface is estimated. It can be shown that the benefical effect of the modified buffer deposition is mainly due to a reduced acceptor concentration at the absorber/buffer interface.

Promoting external inosculation of prevascularised tissue constructs by pre-cultivation in an angiogenic extracellular matrix

The engineering of preformed microvessels offers the promising opportunity to rapidly vascularise implanted tissue constructs by the process of inosculation. Herein, we analyzed whether this process may further be accelerated by cultivation of prevascularised tissue constructs in Matrigel before implantation. Nano-size hydroxyapatite particles/poly(ester-urethane) scaffolds were implanted into the flank of FVB/N-TgN (Tie2/GFP) 287 Sato mice to allow the ingrowth of a granulation tissue with green fluorescent protein (GFP)-positive blood vessels. After harvesting, these prevascularised constructs were then transferred into dorsal skinfold chambers of FVB/N recipient mice to study the process of inosculation. The constructs were implanted directly after embedding in Matrigel or after 3 days of cultivation in the extracellular matrix. Matrigel-free constructs served as control. Cultivation in Matrigel resulted in the outgrowth of CD31/GFP-positive vascular sprouts. Vascularisation of these constructs was markedly improved when compared to the other two groups, as indicated by a significantly elevated functional microvessel density between days 6 to 14 after implantation into the dorsal skinfold chamber. This was associated with an increased number of GFP-positive blood vessels growing into the surrounding host tissue. Thus, the blood supply to prevascularised tissue constructs can be accelerated by their pre-cultivation in an angiogenic extracellular matrix, promoting external inosculation of the preformed microvascular networks with the host microvasculature.

Measurement of stochastic entropy production

Using fluorescence spectroscopy we directly measure entropy production of a single two-level system realized experimentally as an optically driven defect center in diamond. We exploit a recent suggestion to define entropy on the level of a single stochastic trajectory [Seifert, Phys. Rev. Lett. 95, 040602 (2005)10.1103/PhysRevLett.95.040602]. Entropy production can then be split into one of the system itself and one of the surrounding medium. We demonstrate that the total entropy production obeys various exact relations for finite time trajectories.

Early recovery, cognitive function and costs of a desflurane inhalational vs. a total intravenous anaesthesia regimen in long-term surgery

BACKGROUND

The purpose of the study was to compare time of recovery, return of cognitive function, post-anaesthetic care unit (PACU) stay and costs of a propofol/remifentanil (TIVA) with a desflurane/fentanyl-based anaesthesia (desflurane group) in surgical procedures lasting more than 150 min.

METHODS

Forty-nine patients undergoing elective abdominal prostatectomy were allocated randomly to receive bispectal index (BIS)-controlled desflurane/fentanyl (n=24) or propofol/remifentanil (n=25). Awakening, clinical recovery, direct drug acquisition and post-operative pain treatment were documented. Cognitive skills were tested using the Mini-Mental Status (MMST) test.

RESULTS

Extubation was significantly faster with desflurane (6.9+/-3.5 min) than with TIVA (11.2+/-4.0 min) as well as times for stating name and date of birth (desflurane: 6.1+/-3.9 and 6.6+/-4.0 min; TIVA: 12.4+/-11.5 min and 13.4+/-11.3 min). There were no significant differences in PACU discharge times or MMS scores between the groups. Significantly more patients suffered post-operative nausea and vomiting (PONV) in the desflurane (33% vs. 0%) than the TIVA group. Overall costs were significantly higher in the TIVA (58.8+/-11.6 euro) than in the desflurane group (35.0+/-5.7 euro).

CONCLUSION

Patients undergoing prolonged surgical procedures showed a faster early recovery after desflurane/fentanyl than using TIVA, whereas stay in the PACU and recovery of cognitive function were similar in both groups. Costs of a TIVA regimen were significantly higher than using a desflurane-based anaesthesia technique.

Experimental test of the fluctuation theorem for a driven two-level system with time-dependent rates

A single defect center in diamond periodically excited by a laser is shown to provide a simple realization for a system obeying a fluctuation theorem for nonthermal noise. The distribution of these fluctuations is distinctly non-Gaussian, which has also been verified by numerical calculation. For driving protocols symmetric under time reversal a more restricted form of the theorem holds, which is also known from entropy fluctuations caused by thermal noise.

Single molecule spectroscopy on the light-harvesting complex II of higher plants

Spectroscopic and polarization properties of single light-harvesting complexes of higher plants (LHC-II) were studied at both room temperature and T < 5 K. Monomeric complexes emit roughly linearly polarized fluorescence light thus indicating the existence of only one emitting state. Most probably this observation is explained by efficient triplet quenching restricted to one chlorophyll a (Chl a) molecule or by rather irreversible energy transfer within the pool of Chl a molecules. LHC-II complexes in the trimeric (native) arrangement bleach in a number of steps, suggesting localization of excitations within the monomeric subunits. Interpretation of the fluorescence polarization properties of trimers requires the assumption of transition dipole moments tilted out of the symmetry plane of the complex. Low-temperature fluorescence emission of trimers is characterized by several narrow spectral lines. Even at lowest excitation intensities, we observed considerable spectral diffusion most probably due to low temperature protein dynamics. These results also indicate weak interaction between Chls belonging to different monomeric subunits within the trimer thus leading to a localization of excitations within the monomer. The experimental results demonstrate the feasibility of polarization sensitive studies on single LHC-II complexes and suggest an application for determination of the Chl transition-dipole moment orientations, a key issue in understanding the structure-function relationships.

[Psychopathology of drug dependent patients following detoxification]

Abuse of and dependence on drugs are harmful both to the individual and society. The earlier treatment is initiated the better for the patient. Acute treatment is applied on an inpatient basis and involves detoxification and a careful diagnostic work-up conducted in the sober patient. On the basis of an analysis of the patients seen in a single year at a forensic hospital, psychiatric disorders, the sequelae of dependence and organic brain disturbances are described. Addicts with accompanying neuropsychiatric diseases or mental disorders caused by a direct toxic effect or indirectly (e.g. as a result of an accident) are often not capable of taking part in rehabilitation programs for "uncomplicated" addicts. Measures aimed at the prevention of addiction must be intensified.

Mammographic feature enhancement by multiscale analysis

Introduces a novel approach for accomplishing mammographic feature analysis by overcomplete multiresolution representations. The authors show that efficient representations may be identified within a continuum of scale-space and used to enhance features of importance to mammography. Methods of contrast enhancement are described based on three overcomplete multiscale representations: 1) the dyadic wavelet transform (separable), 2) the phi-transform (nonseparable, nonorthogonal), and 3) the hexagonal wavelet transform (nonseparable). Multiscale edges identified within distinct levels of transform space provide local support for image enhancement. Mammograms are reconstructed from wavelet coefficients modified at one or more levels by local and global nonlinear operators. In each case, edges and gain parameters are identified adaptively by a measure of energy within each level of scale-space. The authors show quantitatively that transform coefficients, modified by adaptive nonlinear operators, can make more obvious unseen or barely seen features of mammography without requiring additional radiation. The authors' results are compared with traditional image enhancement techniques by measuring the local contrast of known mammographic features. They demonstrate that features extracted from multiresolution representations can provide an adaptive mechanism for accomplishing local contrast enhancement. By improving the visualization of breast pathology, one can improve chances of early detection while requiring less time to evaluate mammograms for most patients.

Basic concepts of treatment and rehabilitation of drug dependence and how they are counteracted by the legalizing debate

Basic treatment of drug dependent patients begins with detoxification and diagnosis of drug related and drug induced diseases. The therapeutic approach has to be oriented on the career of drug addiction itself and constitutional psychopathology. Patients must undergo specialized care if the drug dependence is complicated by accompanying diseases. All patients experience a life without drugs on rehabilitation programs. Treatment is defined both by a highly structured milieu and by the intention of getting the patient acquainted to a self-determined life. Subsequently, a carefully designed follow-up program is needed. Present debates about legalization of drugs diminish the readiness of the youth to do without drugs.

[The normal electrocardiogram of miniature swine]

Mean normal values for heart rate of 111 (64-190) actions/min, for duration of the PR-interval of 88 (63-120) ms, for the QRS-complex of 36 (26-46) ms and the QT-interval of 252 (183-353) ms were determined from the ECG in 204 male and female Göttinger mini-pigs (mean body weight 12.4 kg). The mean total amplitudes (voltages) of QRSI-III amount to 0.8, 0.9 and 1.1 mV. Considering leads I, II and III positive P-waves are most frequently found in II with 91% and negative ones in III with 23%. Positive T-waves appear in III with 86% and negative ones in I with 88% most frequently. The main polarity of QRS is most frequently positive in I with 56% and negative in III with 48%. The incidence of Q is highest in lead I with 71%, that one of S in II with 55%. The T-waves are mostly discordant with QRS, especially in I with 54%, more seldom concordant yet frequently in II with 30%. A significant negative correlation (r = -0.77) is evident between heart rate and QT-duration, slight negative correlations also exist between heart rate and PR- as well as QRS-duration. The mean angle a QRS from I, II, III and aVR, aVL, aVF in the frontal plane (direction of the cardiac vector; n = 35) amounts to -47 degrees (-150 degrees to +165 degrees). The position of the heart axis is more sagittal with a characteristic deviation of the electrical from the anatomical axis of the heart. Concerning the observed parameters there is also a less intraindividual variability in investigations in series besides the considerable interindividual one. Examples for physiological specialities or variations from the norm of rhythm and configuration of the ECG typical for the miniature pig are presented and discussed.

Proximate determinants of fertility in the Kathmandu Valley, Nepal: an anthropological case study

This article employs the analytical model of Bongaarts and Potter to compare the proximate determinants of fertility among three populations in Nepal's Kathmandu valley with the following characteristics: (1) high and low caste, (2) urban and urban fringe residence, and (3) users and non-users of contraception. It is shown that while Nepal, as a whole, is firmly entrenched in Phase 1 of the fertility transition, each of the populations studied has begun to experience a demographic transition to different degrees. In fact, greater progress in controlling fertility has been made than previously known.

Social and economic forces affecting intergenerational relations in extended families in a Third World country: a cautionary tale from South Asia

This paper questions the implicit assumption derived from modernization theory that elderly persons in the Third World lead secure and satisfying lives because they still live in extended families. Data from elderly Hindus living in Kathmandu, Nepal, are presented and demonstrate that, although these elderly people do continue to live in extended families, social and economic changes have transformed the nature of intergenerational social relations within these families to the detriment of the elderly family members.

[Follow-up control after long-term withdrawal therapy in heroin and multiple drug addicts]

A follow-up study was done in 31 rehabilitation probands who were discharged consecutively from a long term drug withdrawal centre for heroin and multiple drug addiction. Referral had been on the basis of section 64 of the penal code and a motivation for treatment had to be established first. After discharge the majority of probands could be reassessed repeatedly. A total of 180 follow-up investigations included also urinanalysis and in 170 of these cannabinoids were looked for. Cannabis was detected in only two cases. When other addictives were demonstrated in a few cases they could be attributed to codeine-containing medicines beyond doubt. Regular follow-up assessments of past drug addicts including urinanalyses serve for further stabilisation of the patients and at the same time indicate long-term success of treatment.