Trap-integrated fluorescence detection with silicon photomultipliers for sympathetic laser cooling in a cryogenic Penning trap

We present a fluorescence-detection system for laser-cooled 9Be+ ions based on silicon photomultipliers (SiPMs) operated at 4 K and integrated into our cryogenic 1.9 T multi-Penning-trap system. Our approach enables fluorescence detection in a hermetically sealed cryogenic Penning-trap chamber with limited optical access, where state-of-the-art detection using a telescope and photomultipliers at room temperature would be extremely difficult. We characterize the properties of the SiPM in a cryocooler at 4 K, where we measure a dark count rate below 1 s-1 and a detection efficiency of 2.5(3)%. We further discuss the design of our cryogenic fluorescence-detection trap and analyze the performance of our detection system by fluorescence spectroscopy of 9Be+ ion clouds during several runs of our sympathetic laser-cooling experiment.

BASE-STEP: A transportable antiproton reservoir for fundamental interaction studies

Currently, the world's only source of low-energy antiprotons is the AD/ELENA facility located at CERN. To date, all precision measurements on single antiprotons have been conducted at this facility and provide stringent tests of fundamental interactions and their symmetries. However, magnetic field fluctuations from the facility operation limit the precision of upcoming measurements. To overcome this limitation, we have designed the transportable antiproton trap system BASE-STEP to relocate antiprotons to laboratories with a calm magnetic environment. We anticipate that the transportable antiproton trap will facilitate enhanced tests of charge, parity, and time-reversal invariance with antiprotons and provide new experimental possibilities of using transported antiprotons and other accelerator-produced exotic ions. We present here the technical design of the transportable trap system. This includes the transportable superconducting magnet, the cryogenic inlay consisting of the trap stack and detection systems, and the differential pumping section to suppress the residual gas flow into the cryogenic trap chamber.

Ultra-thin polymer foil cryogenic window for antiproton deceleration and storage

We present the design and characterization of a cryogenic window based on an ultra-thin aluminized biaxially oriented polyethylene terephthalate foil at T < 10 K, which can withstand a pressure difference larger than 1 bar at a leak rate <1×10-9 mbar l/s. Its thickness of ∼1.7 μm makes it transparent to various types of particles over a broad energy range. To optimize the transfer of 100 keV antiprotons through the window, we tested the degrading properties of different aluminum coated polymer foils of thicknesses between 900 and 2160 nm, concluding that 1760 nm foil decelerates antiprotons to an average energy of 5 keV. We have also explicitly studied the permeation as a function of coating thickness and temperature and have performed extensive thermal and mechanical endurance and stress tests. Our final design integrated into the experiment has an effective open surface consisting of seven holes with a diameter of 1 mm and will transmit up to 2.5% of the injected 100 keV antiproton beam delivered by the Antiproton Decelerator and Extra Low ENergy Antiproton ring facility of CERN.

Reducing the environmental impact of surgery on a global scale: systematic review and co-prioritization with healthcare workers in 132 countries

BACKGROUND

Healthcare cannot achieve net-zero carbon without addressing operating theatres. The aim of this study was to prioritize feasible interventions to reduce the environmental impact of operating theatres.

METHODS

This study adopted a four-phase Delphi consensus co-prioritization methodology. In phase 1, a systematic review of published interventions and global consultation of perioperative healthcare professionals were used to longlist interventions. In phase 2, iterative thematic analysis consolidated comparable interventions into a shortlist. In phase 3, the shortlist was co-prioritized based on patient and clinician views on acceptability, feasibility, and safety. In phase 4, ranked lists of interventions were presented by their relevance to high-income countries and low-middle-income countries.

RESULTS

In phase 1, 43 interventions were identified, which had low uptake in practice according to 3042 professionals globally. In phase 2, a shortlist of 15 intervention domains was generated. In phase 3, interventions were deemed acceptable for more than 90 per cent of patients except for reducing general anaesthesia (84 per cent) and re-sterilization of 'single-use' consumables (86 per cent). In phase 4, the top three shortlisted interventions for high-income countries were: introducing recycling; reducing use of anaesthetic gases; and appropriate clinical waste processing. In phase 4, the top three shortlisted interventions for low-middle-income countries were: introducing reusable surgical devices; reducing use of consumables; and reducing the use of general anaesthesia.

CONCLUSION

This is a step toward environmentally sustainable operating environments with actionable interventions applicable to both high- and low-middle-income countries.

Suppression of natural lens fluorescence in fundus autofluorescence measurements: review of hardware solutions

Fluorescence lifetime imaging ophthalmoscopy (FLIO), a technique for investigating metabolic changes in the eye ground, can reveal the first signs of diseases related to metabolism. The fluorescence of the natural lens overlies the fundus fluorescence. Although the influence of natural lens fluorescence can be somewhat decreased with mathematical models, excluding this influence during the measurement by using hardware enables more exact estimation of the fundus fluorescence. Here, we analyze four 1-photon excitation hardware solutions to suppress the influence of natural lens fluorescence: aperture stop separation, confocal scanning laser ophthalmoscopy, combined confocal scanning laser ophthalmoscopy and aperture stop separation, and dual point confocal scanning laser ophthalmoscopy. The effect of each principle is demonstrated in examples. The best suppression is provided by the dual point principle, realized with a confocal scanning laser ophthalmoscope. In this case, in addition to the fluorescence of the whole eye, the fluorescence of the anterior part of the eye is detected from a non-excited spot of the fundus. The intensity and time-resolved fluorescence spectral data of the fundus are derived through the subtraction of the simultaneously measured fluorescence of the excited and non-excited spots. Advantages of future 2-photon fluorescence excitation are also discussed. This study provides the first quantitative evaluation of hardware principles to suppress the fluorescence of the natural lens during measurements of fundus autofluorescence.

Immediate coiling of a gastroduodenal arterial bleeding in a case of haemorrhagic shock without haematemesis, a case report

Introduction

and importance: Upper gastrointestinal (GI) bleeding is common in the clinic. In combination with haemorrhagic shock, morbidity is high. Rapid diagnosis and treatment can save lives. With the introduction of precision imaging several treatment options are feasible. Up-to-date diagnosis and treatment requires expertise from interventional radiology, gastroenterology and surgery to form a dedicated intervention team. This is illustrated by a typical case.

Case presentation

We report a 78-year-old otherwise healthy male with a severe diverticulum bleeding. He was initially diagnosed with acute pancreatitis. Approximately 60 minutes after CT scanning, he became haemodynamically instable. He also vomited coffee-like fluid but no clear blood or clots. A repeated CT scan showed active bleeding in the retroperitoneal space highly suspicious for a diverticular bleeding just outside the lumen of the duodenum. An acute multidisciplinary intervention team immediately decided not to perform endoscopy (according to the upper GI bleeding guidelines) but to extend the imaging procedure with digital subtraction angiography (DSA). By this time, active bleeding from a side branch of the gastroduodenal artery was noted and successfully coiled.

Clinical discussion

Guidelines determine day-to-day management in clinical medicine. Still, there is an exception to every rule. The case presented here was typical of upper GI bleeding with haemodynamic instability and signs of shock, but without haematemesis. This combination indicated a bleeding from somewhere outside the lumen of the GI tract. Instead of endoscopy, the acute intervention team decided to perform CT angiography (CTa) with subsequent DSA. On imaging, the bleeding focus was immediately identified and treated by coiling.

Conclusion

Performance of CTa immediately followed by DSA and no endoscopy was decided by an acute intervention team in a patient with upper GI bleeding and haemorrhagic shock. Swift coiling of the bleeding artery outside the GI tract lumen was successful. The team in charge relied on a hybrid multifunctional unit fully equipped to perform interventional radiologic as well as GI procedures.

•

Direct computed tomography angiography could be an option in case the patient vomits no pure blood.

•

Multidisciplinary revaluation is essential in an unstable patient with an upper GI bleeding until the situation is stabilized.

•

The role of coiling is growing, with this important technic a laparotomy could be avoid.

[Iatrogenic cecal perforation two days after a caesarian section]

A 32-year-old healthy woman was seen two days after a complicated c-section with abdominal pain and vomiting. Inflammatory parameters were high and imaging showed a dilatated colon with intestinal pneumatosis. Surgical exploration showed an iatrogenic perforation of the coecum. Therefore, an ileocecal resection with primary anastomosis was performed. Full recovery occurred two weeks later.

Iatrogenic caecal perforation two days after a caesarean section, a case report

INTRODUCTION

and importance: The caesarean section is a widely spread procedure and 29.7 million times performed every year inn 169 countries in the world. Overall, complications are seen in 6% for elective caesarean to 15% for emergency caesarean.

CASE PRESENTATION

We here report a case which was initially diagnosed as a postoperative paralytic ileus. After a complicated caesarean section caused by bleeding and problems with haemostasis, a healthy child was born with full mother recovery for the first 24 hours after surgery. Unfortunately, her condition deteriorated between 24 and 48 hours and she reported progressive nausea and painful bloating. Laboratory tests and CT imaging showed progressive signs of inflammation and distention of the caecum and colon. A second CT scan the next day revealed signs of perforation. An ileocecal resection was performed with a primary anastomosis. Full recovery occurred two weeks later.

CLINICAL DISCUSSION

With an estimated incidence of only 0,08%, bowel perforations due to caesarean section, are rare. Moreover, is the clinical presentation diverse and computed topography is essential during the diagnostic process. To avoid potential morbidity and mortality, the surgeon must consider performing a laparotomy in case of a deteriorating patient in non-invasive treatment fails.

CONCLUSION

Caecal perforation must be considered as complication after a caesarean section. An ileocecal resection is necessary in this situation. This case report shows that a primary anastomosis is a possible option in a healthy patient that is hemodynamically stable during the operation. In case of an unhealthy or hemodynamic unstable patient, the safest option is a temporary ileostomy.

Pretreatment Risk Stratification for Endoscopic Kidney-sparing Surgery in Upper Tract Urothelial Carcinoma: An International Collaborative Study

BACKGROUND

Several groups have proposed features to identify low-risk patients who may benefit from endoscopic kidney-sparing surgery in upper tract urothelial carcinoma (UTUC).

OBJECTIVE

To evaluate standard risk stratification features, develop an optimal model to identify ≥pT2/N+ stage at radical nephroureterectomy (RNU), and compare it with the existing unvalidated models.

DESIGN, SETTING, AND PARTICIPANTS

This was a collaborative retrospective study that included 1214 patients who underwent ureterorenoscopy with biopsy followed by RNU for nonmetastatic UTUC between 2000 and 2017.

OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS

We performed multiple imputation of chained equations for missing data and multivariable logistic regression analysis with a stepwise selection algorithm to create the optimal predictive model. The area under the curve and a decision curve analysis were used to compare the models.

RESULTS AND LIMITATIONS

Overall, 659 (54.3%) and 555 (45.7%) patients had ≤pT1N0/Nx and ≥pT2/N+ disease, respectively. In the multivariable logistic regression analysis of our model, age (odds ratio [OR] 1.02, 95% confidence interval [CI] 1.0-1.03, p = 0.013), high-grade biopsy (OR 1.81, 95% CI 1.37-2.40, p < 0.001), biopsy cT1+ staging (OR 3.23, 95% CI 1.93-5.41, p < 0.001), preoperative hydronephrosis (OR 1.37 95% CI 1.04-1.80, p = 0.024), tumor size (OR 1.09, 95% CI 1.01-1.17, p = 0.029), invasion on imaging (OR 5.10, 95% CI 3.32-7.81, p < 0.001), and sessile architecture (OR 2.31, 95% CI 1.58-3.36, p < 0.001) were significantly associated with ≥pT2/pN+ disease. Compared with the existing models, our model had the highest performance accuracy (75% vs 66-71%) and an additional clinical net reduction (four per 100 patients).

CONCLUSIONS

Our proposed risk-stratification model predicts the risk of harboring ≥pT2/N+ UTUC with reliable accuracy and a clinical net benefit outperforming the current risk-stratification models.

PATIENT SUMMARY

We developed a risk stratification model to better identify patients for endoscopic kidney-sparing surgery in upper tract urothelial carcinoma.

Novel Classification for Upper Tract Urothelial Carcinoma to Better Risk-stratify Patients Eligible for Kidney-sparing Strategies: An International Collaborative Study

BACKGROUND

The European Association of Urology risk stratification dichotomizes patients with upper tract urothelial carcinoma (UTUC) into two risk categories.

OBJECTIVE

To evaluate the predictive value of a new classification to better risk stratify patients eligible for kidney-sparing surgery (KSS).

DESIGN, SETTING, AND PARTICIPANTS

This was a retrospective study including 1214 patients from 21 centers who underwent ureterorenoscopy (URS) with biopsy followed by radical nephroureterectomy (RNU) for nonmetastatic UTUC between 2000 and 2017.

OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS

A multivariate logistic regression analysis identified predictors of muscle invasion (≥pT2) at RNU. The Youden index was used to identify cutoff points.

RESULTS AND LIMITATIONS

A total of 811 patients (67%) were male and the median age was 71 yr (interquartile range 63-77). The presence of non-organ-confined disease on preoperative imaging (p < 0.0001), sessile tumor (p < 0.0001), hydronephrosis (p = 0.0003), high-grade cytology (p = 0.0043), or biopsy (p = 0.0174) and higher age at diagnosis (p = 0.029) were independently associated with ≥pT2 at RNU. Tumor size was significantly associated with ≥pT2 disease only in univariate analysis with a cutoff of 2 cm. Tumor size and all significant categorical variables defined the high-risk category. Tumor multifocality and a history of radical cystectomy help to dichotomize between low-risk and intermediate-risk categories. The odds ratio for muscle invasion were 5.5 (95% confidence interval [CI] 1.3-24.0; p = 0.023) for intermediate risk versus low risk, and 12.7 (95% CI 3.0-54.5; p = 0.0006) for high risk versus low risk. Limitations include the retrospective design and selection bias (all patients underwent RNU).

CONCLUSIONS

Patients with low-risk UTUC represent ideal candidates for KSS, while some patients with intermediate-risk UTUC may also be considered. This classification needs further prospective validation and may help stratification in clinical trial design.

PATIENT SUMMARY

We investigated factors predicting stage 2 or greater cancer of the upper urinary tract at the time of surgery for ureter and kidney removal and designed a new risk stratification. Patients with low or intermediate risk may be eligible for kidney-sparing surgery with close follow-up. Our classification scheme needs further validation based on cancer outcomes.

A case of paramyotonia congenita in pregnancy

Paramyotonia congenita is a rare autosomal dominant non-dystrophic myopathy caused by mutations in the SNC4A gene, which encodes for the voltage-gated sodium channel in skeletal muscle. Symptom onset is typically during early childhood and is characterised by myotonia followed by flaccid paralysis or weakness, usually exacerbated by repeated muscle contractions or cold temperatures. Pregnancy has been reported to increase symptoms of myotonia; however, there is limited information in the literature regarding the possible effects of paramyotonia congenita on pregnancy and labour. We present a successful case of a 20-year-old primigravida with confirmed paramyotonia congenita and review the literature regarding paramyotonia congenita during pregnancy.

Comparison of algorithms to suppress artifacts from the natural lens in fluorescence lifetime imaging ophthalmoscopy (FLIO)

Fluorescence lifetime imaging ophthalmoscopy (FLIO) has developed as a new diagnostic tool in ophthalmology. FLIO measurements are taken from 30° retinal fields in two spectral channels (short spectral channel (SSC): 498-560 nm, long spectral channel (LSC): 560-720 nm). Because of the layered structure of the eye, the detected signal is an interaction of the fluorescence decay of the anterior part and of the fundus. By comparing FLIO measurements before and after cataract surgery, the impact of the natural lens was proven, despite the application of a confocal laser scanning (cSLO) technique. The goal of this work was to determine the best algorithmic solution to isolate the sole fundus fluorescence lifetime from the measured signal, suppressing artifacts from the natural lens. Three principles based on a tri-exponential model were investigated: a tailfit, a layer-based approach with a temporally shifted component, and the inclusion of a separately measured fluorescence decay of the natural lens. The mean fluorescence lifetime τ_m,12 is calculated using only the shortest and the intermediate exponential component. τ_m,all is calculated using all three exponential components. The results of tri-exponential tailfit after cataract surgery were considered as a reference, because the implanted artificial lens can be assumed as non-fluorescent. In SSC, the best accordance of τ_m,all of the reference was determined with τ_m,12 of the tailfit before surgery. If high-quality natural lens measurements are available, the correspondence of τ_m,12 is best with τ_m,all of the reference. In LSC, there is a good accordance for all models between τ_m,12 before and after surgery. To study the pure fundus fluorescence decay in eyes with natural lenses, we advise to utilize fluorescence lifetime τ_m,12 of a triple-exponential tailfit, as it corresponds well with the mean fluorescence lifetime τ_m,all of eyes with fluorescence-less artificial intraocular lenses.

System Xc- Antiporter Inhibitors: Azo-Linked Amino-Naphthyl-Sulfonate Analogues of Sulfasalazine

The cystine/glutamate antiporter system Xc- (SXc-) mediates the exchange of intracellular L-glutamate (L-Glu) with extracellular L-cystine (L-Cys2). Both the import of L-Cys2 and the export of L-Glu take on added significance in CNS cells, especially astrocytes. When the relative activity of SXc- overwhelms the regulatory capacity of the EAATs, the efflux of L-Glu through the antiporter can be significant enough to trigger excitotoxic pathology, as is thought to occur in glioblastoma. This has prompted considerable interest in the pharmacological specificity of SXc- and the development of inhibitors. The present study explores a series of analogues that are structurally related to sulfasalazine, a widely employed inhibitor of SXc-. We identify a number of novel aryl-substituted amino-naphthylsulfonate analogues that inhibit SXc- more potently than sulfasalazine. Interestingly, the inhibitors switch from a competitive to noncompetitive mechanism with increased length and lipophilic substitutions, a structure-activity relationship that was previously observed with aryl-substituted isoxazole. These results suggest that the two classes of inhibitors may interact with some of the same domains on the antiporter protein and that the substrate and inhibitor binding sites may be in close proximity to one another. Molecular modeling is used to explore this possibility.

[Fracture prevention in metastatic prostate cancer]

Patients with metastatic prostate cancer are living longer than they used to, thanks to a wider range of therapeutic options. This means that an increasing number of men will receive long-term treatment with anti-hormonal therapy - androgen-deprivation therapy (ADT) - and the risk of side effects from this therapy is increasing. A relevant decrease in bone density is increasingly seen in patients receiving ADT, which means that a disproportionate increase in risk of fractures is seen in aging patients. Urologists are confronted with these patients in clinical practice. The question is how urologist-care for these patients is organised in the Netherlands. A survey among urologists in the Netherlands revealed that there is great diversity in how they think and act, and that there is a need for national guidelines and additional training on this subject.

Antiglycine receptor antibody related disease: a case series and literature review

BACKGROUND AND PURPOSE

Antibodies to glycine receptors (GlyR-Abs) were first defined in progressive encephalopathy with rigidity and myoclonus (PERM) but were subsequently identified in other clinical presentations. Our aim was to assess the clinical associations of all patients identified with GlyR-Abs in Queensland, Australia, between April 2014 and May 2017 and to compare these to cases reported in the literature.

METHODS

A literature review identified the clinical features of all published GlyR-Ab-positive cases through online databases. A case series was undertaken via collection of clinical information from all patients diagnosed or known to immunology, pathology or neurological services in Queensland during the study period of 3 years.

RESULTS

In all, 187 GlyR-Ab-positive cases were identified in the literature. The majority (47.6%) had PERM, 22.4% had epilepsy, but the remaining 30% included mixed phenotypes consisting of cerebellar ataxia, movement disorders, demyelination and encephalitis/cognitive dysfunction. By contrast, in our series of 14 cases, eight had clinical presentations consistent with seizures and epilepsy and only three cases had classical features of PERM. There was one case each of global fatiguable weakness with sustained clonus, laryngeal dystonia and movement disorder with hemiballismus and tics. The rate of response to immune therapy was similar in all groups.

CONCLUSION

Antibodies to glycine receptors are linked to a spectrum of neurological disease. The results of the literature review and our case series suggest a greater relationship between GlyR-Abs and epilepsy than previously reported.

Multisubstance Analysis of Reflection Spectra before and after Laser Photocoagulation for Proliferative Diabetic Retinopathy

Purpose

The aim of the study was to provide new data that add to the understanding of diabetic retinopathy and its treatment by photocoagulation.

Patients and Methods.

Using a spectrometric method, the reflection spectra of the macula in six type II diabetics with proliferative diabetic retinopathy were measured before and after laser photocoagulation and compared with normals. The investigations were done one day before laser photocoagulation and again the day after. Further measurements were made 14 days, 6 weeks and 4 months after coagulation. The reflection spectra were assessed by multisubstance analysis.

Results and Conclusions.

The contents of xanthophyll, melanin and choroidal oxyhemoglobin and the intensity of scattered light were significantly altered after laser coagulation. For example, in patients with proliferative diabetic retinopathy the content of oxyhemoglobin in the choroid was lower than normal, but it rose after laser treatment. This suggests an improved oxygen supply of the choroid after laser coagulation, implying reduced retinal hypoxia.

1,3,5-Tris(dimethylamino)benzol mit Iod und 1,3,5-Tricyanobenzol: Eine ungewöhnliche Dimerisierung und ein „normaler“ Donor/Akzeptor-Komplex / 1,3,5-Tris(dimethylamino)benzene with Iodine and 1,3,5-Tricyanobenzene: An Unusual Dimerization and a “Normal” Donor/Acceptor-Complex

Reaction of 1,3,5-tris(dimethylamino)benzene (TDMAB) with iodine in solution gives dark red needles of a compound (1) with stoichiometry C24H42I6N6, Mr = 1176.07, orthorhombic, Cmca, Z = 4, a = 10.865(2) Å, b = 16.737(6) Å. c = 20.511(9) Å, V = 3730 Å3, dc = 2.1 g·cm-3 measured at room temperature, R = 0.062 for 744 independent reflections and 100 L. S.-parameters. The solid contains bis[tris(dimethylamino)cyclohexadienylium]dications - obtained by dimerization of TDMAB+ radical cations - and triiodide counter anions. The solid is diamagnetic.

Reaction of TDMAB with 1,3,5-tricyanobenzene (TCB) leads to orange platelets of 2 with stoichiometry C21H24N6, Mr = 360.4, orthorhombic, Pna21 Z = 4, a = 11.074(4) Å, b = 11.568(4) Å, c = 16.100(7) Å, V = 2060 Å3, dc = 1.18 g·cm-3, measured at room temperature, R = 0.065 for 921 independent reflections and 156 parameters. The solid consists of donor (TDMAB) - acceptor (TCB) pairs. The compound is diamagnetic at room temperature.

Preparation, Structure and Physical Properties of BEDT-TTF* Nitrates

Electrocrystallization of BEDT -TTF in THF with tetrabutylammonium nitrate as supporting electrolyte leads to the deposition of at least three different phases. The a-phase (C10H8S8)3(NO3)2, Mt = 1277.98, crystallizes in the monoclinic space group P21/n. The structure of this solid was solved: a = 5.890(2), b = 31.125(10), c = 12.915(6) Ä , β = 103.73(3)°, V = 2300 Å 3, Z - 2, Dx = 1.84 gem-3, MoKfα λ = 0.7107 Å , μ = 11.2 cm-1, F(000) = 1300, room temperature, R = 0.057 for 1888 observed independent reflections. Sheets of BEDT-TTF radical cations with short intermolecular S···S contacts (>3.315(4) Å ) are separated by anion layers. Two more BEDT-TTF nitrates have been characterized by their unit cell data. Results of temperature dependent electrical conductivity and thermopower measurements on crystals of the a-phase are presented. They are metallic down to about 30 K

Donor/Akzeptor-Komplexe aus 1,3,5-Tris(dimethylamino)benzol und 1,2,3,4,5,6-Hexacyanobenzol/Donor/Acceptor Complexes from 1,3,5-Tris(dimethylamino)benzene with 1,2,3,4,5,6-Hexacyanobenzene

Reaction of 1,3,5-tris(dimethylamino)benzene (TDMAB ) with 1,2,3,4,5,6-hexacyanobenzene (HCNB) in acetonitrile solution gives - depending on the crystallization method - two different products: dark needles of a 1:1 (1) and black compact crystals with a metallic lustre of a 2:1 (2) charge transfer complex. 2 crystallizes in the triclinic space group P1 , Z = 1, a = 9.9489(22), b = 10.0555(21), c = 10.1418(20) Å , α = 115.006(16)°, β = 102.820(17)°, γ = 93.647(18)°, V = 882.3 Å3, dc = 1.2 g cm-3, measured at room temperature, R = 0.053 for 2670 observed independent reflections and 301 parameters. The structure contains isolated “trimers” of one HCNB acceptor which is “pancaked” by two TDMAB neighbors. The arrangement of these trimers in the lattice results in alternating HCNB and TDMAB sheets. The solid is diamagnetic.

1 could not be obtained in crystals suitable for a single crystal X-ray investigation. Its paramagnetism which is observed immediately after preparation disappears in the course of several days.

Transanular Interaction in [2.2]Phanes: [2.2](2,7)Pyrenophane

The emission spectra of [2.2] (2,7) pyrenophane and the zero field splitting parameters D und E of its excited triplet state were measured in glasses and in small single crystals at 1.3 K. The results are being compared with monomer pyrene and 2,7-dimethylpyrene in liquid and solid solutions as well as in single crystals.

Magnetic ordering and charge dynamics in κ-(BEDT-TTF)2Cu[N(CN)2]Cl

The Mott insulator κ-(BEDT-TTF)2Cu[N(CN)2]Cl consists of molecular dimers arranged on an anisotropic triangular lattice. At low temperatures a pronounced dielectric anomaly is observed, and eventually a canted antiferromagnetic ground state forms. Optical spectroscopy clearly rules out charge imbalance and the existence of quantum electric dipoles with a dipolar-spin coupling. Here we suggest a novel form of spin-charge coupling where the prominent in-plane dielectric response in κ-(BEDT-TTF)2Cu[N(CN)2]Cl is explained by short-range discommensurations of the antiferromagnetic phase in the temperature range 30 K < T < 50 K, and by relaxation of charged domain walls in the ferromagnetic structure at lower temperatures.

Collective excitations in the charge-ordered phase of α-(BEDT-TTF)2I3

The charge response of a charge-ordered state in the organic conductor α-(BEDT-TTF)2I3 is characterized by dc resistivity, dielectric and optical spectroscopy in different crystallographic directions within the two-dimensional conduction layer. Two dielectric modes are detected. The large mode is related to the phasonlike excitation of the 2k(F) bond-charge density wave which forms in the ab plane. The small dielectric mode is associated with the motion of domain-wall pairs along the a and b axes between two types of domains which are created due to inversion symmetry breaking.

Towards metabolic mapping of the human retina

Functional alterations are first signs of a starting pathological process. A device that measures parameter for the characterization of the metabolism at the human eye-ground would be a helpful tool for early diagnostics in stages when alterations are yet reversible. Measurements of blood flow and of oxygen saturation are necessary but not sufficient. The new technique of auto-fluorescence lifetime measurement (FLIM) opens in combination with selected excitation and emission ranges the possibility for metabolic mapping. FLIM not only adds an additional discrimination parameter to distinguish different fluorophores but also resolves different quenching states of the same fluorophore. Because of its high sensitivity and high temporal resolution, its capability to resolve multi-exponential decay functions, and its easy combination with laser scanner ophthalmoscopy, multi-dimensional time-correlated single photon counting was used for fundus imaging. An optimized set up for in vivo lifetime measurements at the human eye-ground will be explained. In this, the fundus fluorescence is excited at 446 or 468 nm and the time-resolved autofluorescence is detected in two spectral ranges between 510 and 560 nm as well as between 560 and 700 nm simultaneously. Exciting the fundus at 446 nm, several fluorescence maxima of lifetime t1 were detected between 100 and 220 ps in lifetime histograms of 40 degrees fundus images. In contrast, excitation at 468 nm results in a single maximum of lifetime t1 = 190 +/- 16 ps. Several fundus layers contribute to the fluorescence intensity in the short-wave emission range 510-560 nm. In contrast, the fluorescence intensity in the long-wave emission range between 560 and 700 nm is dominated by the fluorescence of lipofuscin in the retinal pigment epithelium. Comparing the lateral distribution of parameters of a tri-exponential model function in lifetime images of the fundus with the layered anatomical fundus structure, the shortest component (t1 = 190 ps) originates from the retinal pigment epithelium and the second lifetime (t2 = 1,000 ps) from the neural retina. The lifetime t3 approximately 5.5 ns might be influenced by the long decay of the fluorescence in the crystalline lens. In vitro analysis of the spectral properties of expected fluorophores under the condition of the living eye lightens the interpretation of in vivo measurements. Taking into account the transmission of the ocular media, the excitation of NADH is unlikely at the fundus.

Anomalous lattice response at the Mott transition in a quasi-2D organic conductor

Discontinuous changes of the lattice parameters at the Mott metal-insulator transition are detected by high-resolution dilatometry on deuterated crystals of the layered organic conductor kappa-(BEDT-TTF)(2)Cu[N(CN)(2)]Br. The uniaxial expansivities uncover a striking and unexpected anisotropy, notably a zero effect along the in-plane c axis along which the electronic interactions are relatively strong. A huge thermal expansion anomaly is observed near the end point of the first-order transition line enabling us to explore the critical behavior with very high sensitivity. The analysis yields critical fluctuations with an exponent alpha approximately 0.8+/-0.15 at odds with the novel criticality recently proposed for these materials [Kagawa et al., Nature (London) 436, 534 (2005)]. Our data suggest an intricate role of the lattice degrees of freedom in the Mott transition for the present materials.

[Change of retinal oxygen saturation in healthy subjects and in early stages of diabetic retinopathy during breathing of 100% oxygen]

BACKGROUND

Disturbances in the microcirculation are a source of retinal diabetic alterations. Comprehensive studies of blood flow parameters have been performed, but it is not known how ageing, duration of diabetes, blood sugar, glycolysed haemoglobin and elevated systemic blood pressure act in the early stages of diabetic retinopathy.

MATERIAL AND METHODS

The arterial and venous oxygen saturation (aOS, vOS) were measured with a Jena Ophthalmo Spectrometer in 28 healthy subjects (NP) (30.3 +/- 13.1 years), 31 Type I diabetics (T I) (42.2 +/- 12.9 years), and in 25 Type II diabetics (T II) (58.9 +/- 6.9 years), suffering form mild or moderate non-proliferative diabetic retinopathy, before, during breathing of 100 % oxygen for 6 minutes, and after respiration of air during 10 minutes.

RESULTS

Before oxygen breathing, the venous oxygen saturation in diabetics increased with age. During breathing of 100 % oxygen, the vOS increased considerably by 20 % in all groups. The arterio-venous difference of oxygen saturation was decreased with age in diabetics, but there was no dependence on age in normals. In Type II diabetics, the vOS before oxygen breathing was increased with HbA1c. There was also a positive correlation between vOS and blood pressure before oxygen breathing.

CONCLUSION

Healthy subjects and diabetics in the early stages of diabetic retinopathy exhibit comparable changes of oxygen saturation during breathing of 100 % oxygen. Measurements of venous OS are most evident. First differences were detectable between diabetics and normals in the normalisation after oxygen respiration.

Fundusspektrometrie bei altersbezogener Makulopathie

BACKGROUND

Spectroscopic methods permit the non-invasive detection of fundus pigments by the wavelength-dependent absorption of fluorescence as well as by the fluorescence lifetime. From the relative concentrations of haemoglobin and oxyhaemoglobin, the oxygen saturation can be calculated. The onset of age-related maculopathy might be delayed by a high optical density of xanthophyll. The detection of alterations in fundus autofluorescence points to age-related pathomechanisms (accumulation of lipofuscin, formation of connective tissue). The detection of autofluorescence of redox-pairs of coenzymes results in information about metabolic states at the cellular level, and might make possible an early detection of age-related changes when they are still reversible.

METHOD

The evaluation of reflectance spectra, detected by imaging ophthalmo-spectrometry, results in the calculation of oxygen saturation or in the optical density of xanthophyll or of melanin. Fluorescence spectra can be measured also by this technique. For the 2-dimensional determination of the distribution of xanthophyll, a very simple method was developed, requiring fundus illumination by one wavelength only. In the detection of time-resolved autofluorescence, the fluorescence lifetime is used for the determination of endogenous fluorophores.

RESULTS

As result of comparing studies between ARM patients and healthy subjects, the consumption of retinal oxygen was increased already in the children of ARM patients. An increasing optical density of xanthophyll was determined after lutein supplementation. Differences in fluorescence lifetime were determined between ARM patients and healthy subjects, but their interpretation requires investigations of cell or of organ model cultures.

CONCLUSIONS

The described methods permit in vivo basic investigations of ARM and can be considered as impulses for the development of diagnostic devices.

[Spectral separation in ocular fundus autofluorescence images in patients suffering from age-related macular degeneration]

INTRODUCTION

Alterations in the intrinsic ocular fundus fluorescence are under discussion particularly in connection with age-related macular degeneration. However, further knowledge of the chemical substrate of fluorescence is necessary.

METHOD

Ocular fundus autofluorescence was observed using a fundus camera. The fluorescence emission was recorded using a 3-chip CCD camera. For comparison, the fluorescence spectra of lipofuscin, A2-E, FAD, NADH(2) and AGE's were recorded by the Jena ophthalmo-spectrometer.

RESULTS

In contrast to the homogeneous intrinsic fluorescence of a normal fundus, the fluorescence images of patients suffering from AMD showed remarkable local differences. The detected fluorescence spectra showed remarkable overlaps.

DISCUSSION

We introduced a new technique enabling the detection of spectral differences in images of ocular fundus autofluorescence. Besides the fluorescence of lipofuscin, we found a green one in patients suffering from nonexudative AMD.

Grenzen der konfokalen Laser Scanning Technik bei Messungen der zeitaufgelösten Autofluoreszenz am Augenhintergrund / Limits of the confocal laser-scanning technique in measurements of time-resolved autofluorescence of the eye-ground

GOAL

The 2-dimensional measurement of the time-dependent autofluorescence has in combination of confocal laser scanner technique and time correlated single photon counting the potential for the investigation of the metabolism state at the eye ground. It was to be examined, to what extent these measurements are influenced through the auto-fluorescence of the crystalline lens.

MATERIAL AND METHOD

The time-dependent auto-fluorescence was measured on eyes of 21 patients with age-related macular degeneration (AMD) and of 26 healthy subjects in 40 degrees fundus images. The experimental set-up used, was developed at the eye clinic of the University of Jena. In this scanning laser ophthalmoscope, the fundus was excited at 446 nm by pulses of 100 ps full width at half maximum and 40 MHz repetition rate. The auto-fluorescence was detected with a time resolution of 25 ps for wavelengths > 500 nm. The dynamic auto-fluorescence of each pixel was approximated by a tri-exponential model function. In order to determine the influence of the fluorescence of the crystalline lens, healthy eyes and eyes were compared with implanted artificial intra-ocular lenses. For comparison the frequency distributions were used, which the decay times t1, t2 and t3 in the fundus images had been calculated with.

RESULTS

Clear differences were shown in the frequency distributions of the fluorescence lifetimes between AMD-patients and healthy subjects, It resulted, however, from a crucial analysis that the fluorescence of the crystalline lens is not suppressed by the confocal laser scanning principle sufficiently. In particular the long lifetime t3 is overlapped by the fluorescence of the crystalline lens of about 4.6 ns. To the complete suppression of the influence of the lens fluorescence in measurements of the time-resolved fundus auto-fluorescence it is suggested to combine the confocal laser scanning technique with the principle of the aperture diaphragm division.

CONCLUSION

In order to be able to determine the capability of measurements of the time-dependent fundus auto-fluorescence as diagnostic tool exactly, the influence of the crystalline lens is to reduce through the combination of confocal laser scanning ophthalmoscopy with the principle of the aperture diaphragm division diversely.

[Alterations in autofluorescence decay time in the fundus after oxygen provocation]

BACKGROUND

Alterations in the equilibrium of redox pairs of co-enzymes give information about the metabolic state in the citric acid cycle as well as in the respiratory chain. Fluorescence properties are different between the reduced and oxidised states of co-enzymes so that a change of the oxygen partial pressure can be sensitively detected in the tissue. Therefore, it was investigated whether the autofluorescence of co-enzymes is detectable in the living fundus.

METHOD

The provocation of metabolism was realised by inspiration of 100% oxygen. The time-resolved autofluorescence was detected by a single photon counting technique. The decay behaviour of autofluorescence was approximated by a bi-exponential model. For evaluation of the results, histograms of decay times tau(1) and tau(2) were calculated in defined ranges around the macula and optic disc before, during, and after inhaling oxygen.

RESULTS

The calculated decay times corresponded in the macula to the decay times of FAD and NADH(+) given in the literature. Connective tissue in the optic disc also showed fluorescence.

CONCLUSIONS

Changes in the histograms of decay rates demonstrate that provocation of metabolism is detectable by measurement of time-resolved autofluorescence. This method reveals the evaluation of metabolism at the cellular level as a new diagnostic possibility.

[Determination of the concentration distribution of macular pigment from reflection and fluorescence images]

OBJECTIVE

The macular pigment xanthophyll protects the macula in two ways: firstly, it absorbs hazardous blue light and secondly, it acts as a radical scavenger. A low concentration of xanthophyll may be regarded as a risk factor for age-related macular degeneration (AMD). Therefore, we investigated a simple method to determine the xanthophyll concentration at the fundus which is suitable for patient screening.

METHOD

The local distribution of xanthophyll density was determined from monochromatic blue reflection images and autofluorescence images of the fundus in 18 healthy volunteers (mean age: 23.9 years). The significance of the parameters maximal, global, and mean concentration were compared.

RESULTS

The maximal optical density of xanthophyll determined from reflection images was found to be 0.29+/-0.08 (mean for all test persons) which is in good agreement with literature data. The total xanthophyll concentration which is proportional to the maximal density, appeared to be appropriate to describe a person's overall xanthophyll status. Because of the low intensity of autofluorescence images, these are less useful for the determination of the xanthophyll concentration.

CONCLUSIONS

Because of it's simplicity, the determination of xanthophyll concentration as described here can be performed by every ophthalmologist using a fundus camera and is, therefore, suitable as a screening method.

[Time-correlated measurement of autofluorescence. A method to detect metabolic changes in the fundus]

The detection of metabolic changes opens the possibility for intervention of reversible pathological alterations. Measurements of oxygen saturation are limited to the blood vessel system. Detection of alterations in oxygen concentrations are up to 3 orders of magnitude more sensitive by autofluorescence of coenzymes than by measurement of oxygen saturation. Because of limited transmission of the ocular media no specific excitation of endogenous fluorophores can be realised. For this reason it was investigated if the fluorescence lifetime after pulse excitation can be detected at the human fundus. Applying a laser scanner ophthalmoscope and mode-locked Ar(+) laser as well as time-correlated single photon counting, lifetime images of the living fundus were obtained. In mono-exponential approximation, a mean lifetime of 5 ns was detected from the optic disc and large vessels whereas about 1.5 ns were detected in the parapapillary area. By evaluating the frequency of lifetimes, lipofuscin, free FAD, and collagen are probably detectable. Comparative measurements were performed in fundus specimens and on free FAD.

[Intrastomal refractive surgery with ultra-short laser pulses. Results from initial in vitro experiments]

PURPOSE

To investigate the possibilities and techniques for intrastromal ablation of the cornea by the use of ultra-short laser pulses.

METHOD

A laser-induced plasma with a diameter of 8 mu was generated 100-300 mu below Bowmans membrane by focussing of a Ti:Saphir laser (lambda=805 nm, pulse width: 115 fs, energy: 0.6-3.3 microJ). Scanning the laser beam enabled arbitrary transsections in the corneal stroma. All experiments were performed in porcine eyes 1-4 h post-mortem.

RESULTS

Two-dimensional sections were achieved applying a minimal laser energy of 0.6 microJ at a separation of the single laser effects of 10 micrometer. A 150 micrometer thick disc was excised 150 micrometer below Bowmans membrane and extracted through a keratotomy performed by the laser. Sharp-cut edges were observed by slit-lamp biomicroscopy.

CONCLUSIONS

Ultra-short laser pulses are suitable for precise intrastromal ablation.

Scattering properties of the retina and the choroids determined from OCT-A-scans

GOAL

To determine the coefficient and the anisotropy of scattering as well as the refractive indices in the retina and in the choroid noninvasively in vivo.

METHODS

The power of coherent reflected light versus fundus depth is recorded in OCT-A-scans. The ratio of refractive indices is derived from the height of the reflection peaks. Provided that the absorption coefficient is known from fundus reflectometry, the scattering coefficient and anisotropy are calculated from the offset and the slope of the signal behind the reflection peaks on the basis of a single backscattering model.

RESULTS

We found scattering coefficients of 12/mm (retina) and 27.5/mm (choroid) as well as anisotropy values of 0.97 (retina) and 0.90 (choroid).

DISCUSSION

The OCT is usually employed for the measurement of intraocular distances. The new technique described here gives the unique opportunity to determine further interesting parameters of single ocular layers. The values given above are in good agreement with in vitro results.

A new method for the measurement of oxygen saturation at the human ocular fundus

Measurements of the transmission and the reflectance spectra of whole blood exhibit a different dependence of the thickness of the blood layer. Whereas the transmission spectra decrease at all wavelengths, in the reflectance two ranges with different behaviour have to distinguish. In the absorption dominated range between about 500 and 600 nm, there is only a marginal influence of the thickness of the blood layer. In contrast, in the scattering dominated range higher than about 600 nm the reflectance increases if the thickness of the blood layer increases. Proofed by Monte Carlo simulation, the reflected light, which will be measured in ophthalmologic devices, consists both of light which penetrates a vessel once and will be reflected at the background and of light which is internally reflected at the blood column. Only in small vessels (diameter < 50 microm) the transmitted part dominates. With increasing diameter of the vessels the internally reflected light dominates. Especially under the conditions of a confocal laser scanner, the transmitted part of light is always small. As the measured light consists of both parts of light, a new model for the approximation of the measured reflected light is given, containing an expression for the transmitted and for the internally reflected light. The model was applied for the approximation of the reflectance of blood in a cuvette with an coloured background, delivering sufficient exact result. The oxygen saturation was determined in 256 measurements of 30 healthy persons using an ophthalmo imaging spectrometer. The mean arterial oxygen saturation was 91 +/- 5%, the mean venous oxygen saturation was 59 +/- 9% and the arterio-venous difference in the oxygen saturation was 35%, which is in good agreement with the arterio-venous difference known in the brain. First measurements of the oxygen saturation in age-related macular degeneration point to partly different pathological changes of the retinal microcirculation in dry and in wet AMD.