Molecular Isomer Identification of Titan's Tholins Organic Aerosols by Photoelectron/Photoion Coincidence Spectroscopy Coupled to VUV Synchrotron Radiation.

The chemical composition of Titan organic haze is poorly known. To address this issue, laboratory analogues named tholins are synthesized and analyzed by methods often requiring an extraction process in a carrier solvent. These methods exclude the analysis of the insoluble tholins' fraction and assume a hypothetical chemical equivalence between soluble and insoluble fractions. In this work, we present a powerful complementary analysis method recently developed on the DESIRS VUV synchrotron beamline at SOLEIL. It involves soft pyrolysis of tholins at ∼230 °C and electron/ion coincidence analysis of the emitted volatile compounds photoionized by tunable synchrotron radiation. By comparison with reference photoelectron spectra (PES), the spectral information collected on the detected molecules yields their isomeric structure. The method is more readily applied to light species (m/z ≤ 69), while for heavier ones, the number of possibilities and the lack of PES reference spectra in the literature limit its analysis. A notable pattern in the analyzed tholins is the presence of species containing adjacent doubly bonded N atoms, which might be a signature of heterogeneous incorporation of N2 in tholins.

Ionization photophysics and spectroscopy of cyanoacetylene.

Photoionization of cyanoacetylene was studied using synchrotron radiation over the non-dissociative ionization excitation range 11-15.6 eV, with photoelectron-photoion coincidence techniques. The absolute ionization cross-section and spectroscopic aspects of the parent ion were recorded. The adiabatic ionization energy of cyanoacetylene was measured as 11.573 ± 0.010 eV. A detailed analysis of photoelectron spectra of HC3N involves new aspects and new assignments of the vibrational components to excitation of the A(2)Σ(+) and B(2)Π states of the cation. Some of the structured autoionization features observed in the 11.94 to 15.5 eV region of the total ion yield (TIY) spectrum were assigned to two Rydberg series converging to the B(2)Π state of HC3N(+). A number of the measured TIY features are suggested to be vibrational components of Rydberg series converging to the C(2)Σ(+) state of HC3N(+) at ≈17.6 eV and others to valence shell transitions of cyanoacetylene in the 11.6-15 eV region. The results of quantum chemical calculations of the cation electronic state geometries, vibrational frequencies and energies, as well as of the C-H dissociation potential energy profiles of the ground and electronic excited states of the ion, are compared with experimental observations. Ionization quantum yields are evaluated and discussed and the problem of adequate calibration of photoionization cross-sections is raised.

Choroidal involvement in patients with catastrophic anti-phospholipid syndrome: Two case reports.

PURPOSE: To describe choroidal involvement in catastrophic antiphospholipid syndrome (CAPS). METHODS: We report here two cases of bilateral CAPS choroidopathy in two female patients. RESULTS: Case report 1: A thirty-five-year-old female patient, with history of primary anti-phospholipid syndrome (APS), treated with anticoagulants, presented an acute renal failure following a salpingectomy. She complained of bilateral acute blurred vision. Ophthalmologic evaluation revealed visual acuity (VA) of 5/10, extensive serous retinal (SRD) detachment, areas of hypofluorescence on fluorescein angiography (FA), and non-perfusion areas in the choriocapillaris, on optical coherence tomography angiography (OCT-A), in both eyes. Considering the diagnosis of probable CAPS, the patient received intravenous pulse steroids, plasmapheresis, intravenous anticoagulation and haemodialysis, with favourable evolution. Case report 2: A thirty-three-year-old female patient, with history of systemic lupus erythematosus (SLE) and secondary APS, treated with corticosteroids, immunosuppressive agents and anti-coagulation, presented a myocardiac infarction. She complained of bilateral acute blurred vision. Ophthalmologic evaluation revealed VA of 1/10 in the RE and 6/10 in LE, bilateral extensive SRD, leakage points on FA and non-perfusion areas in the choriocapillaris on OCT-A. Criteria of probable CAPS were fulfilled. Treatment with intravenous pulse steroids, anticoagulation and reanimation modalities allowed VA improvement. Alveolar haemorrhage and cardiogenic shock led to fatal evolution. CONCLUSION: Our case reports highlight the importance of early diagnosis and ophthalmic evaluation in CAPS. Multidisciplinary approach and rapid initiation of effective treatment, based on corticosteroids, anticoagulation and plasmapheresis, allow better vital and visual prognosis.

Structural rearrangement in the formation of jet-cooled complexes of chiral (S)-1,2,3,4-tetrahydro-3-isoquinolinemethanol with methyl lactate: chirality effect in conformer selection.

The jet-cooled complexes between the two enantiomers of methyl lactate (ML) and (S)-1,2,3,4-tetrahydro-3-isoquinolinemethanol (THIQM) are studied by double resonance spectroscopy combined with ab initio calculations. Both diastereomer complexes exist in different isomers, involving either direct addition of THIQM on ML with no structural rearrangement of the subunits or formation of very stable structures involving multiple intermolecular hydrogen bonds and extensive deformation of the subunits. Competition between these two processes and its dependence upon chirality are discussed. It is shown that the most stable form of the chromophore (THIQMI with an OH···N hydrogen bond) prefers to directly stick to ML to form the addition complex whereas the second conformer (THIQMII with NH···O hydrogen bond) rearranges to form a strongly bound structure. The two structures are formed for the homochiral as well the heterochiral complex, however with different relative abundance. This shows an enantioselective binding preference of ML for one of the conformers of the chromophore.

Surgical management of post-traumatic iris cyst: A case report.

INTRODUCTION AND IMPORTANCE: Cysts of the iridociliary complex could be primary or secondary. Small and asymptomatic iris cysts can be monitored, whereas larger cysts require treatment as they can cause severe complications. Treatment modalities can range from minimally invasive techniques to aggressive surgical procedures. CASE PRESENTATION: We report the case of an 11-year-old child who applied to our department with blurred vision. The anterior segment examination of the right eye revealed an oval, light brown, semi translucid cyst, located in the iris extending to corneal endothelium. The iris cyst was managed surgically. A pigment magma on the anterior surface of the lens was observed and was respected in order not to induce a cataract. Surgical treatment consisted of total removal of the external cyst layer. CLINICAL DISCUSSION: There are numerous different methods for treating iris cysts. The main goal of treatment is to be as little intrusive as possible. Cysts that are small, stable, and asymptomatic can be observed. To avoid major issues, larger cysts may need to be treated. When less intrusive treatments have failed, surgery is always the final option. In our case, the post-traumatic iris cyst was immediately treated surgically by aspiration followed by excision of its wall, because of the significant visual disturbance, the age of the patient, and the corneal endothelial touch. CONCLUSION: Surgical intervention remains the last option, especially when less invasive options did not reveal to be successful due to the extensive nature of the lesion.

Retinal artery macroaneurysm complicated with subhyaloid hemorrhage: two case reports.

The authors report two cases of retinal artery macroaneurysm (RAM) complicated with subhyaloid hemorrhage. There are multiple cases about RAM that have been published; however, none of them present all the different treatments with its benefits and its limitations. Our study highlights all aspects of treatment. RAM is an uncommon pathology that affects generally elderly women with systemic vascular pathologies. It is often unilateral, and the patients stay mostly asymptomatic. Most cases of RAM regress without any treatment. A case of a 54-year-old male, with a medical history of hypertension who presented with an acute and unilateral decreased visual acuity (VA). Initial VA was limited to counting fingers at 1 m in the right eye (RE). The anterior segment was normal in both eyes. A fundus examination in the RE showed a large subhyaloid hemorrhage associated to retinal hemorrhage. Fluorescein angiography in the RE did not reveal any sign of macroaneurysm due to blockage of fluorescein by the hemorrhage. In the left eye, there was a hyperfluorescent paramacular lesion. Optical coherence tomography showed the hyperreflectivity of the subhyaloid hemorrhage and the underlying retinal layers could not be seen. Neodymium-doped yttrium aluminum garnet laser hyaloidotomy was performed for this patient to release the trapped hemorrhage into the vitreous, 3 weeks after initial loss of vision with a good visual outcome after the treatment. An 80-year-old woman, with medical history of rheumatoid arthritis who presented with an acute loss of vision in the RE. VA in the RE was 20/200. She had a nuclear cataract in both eyes. A fundus examination showed a subyaloid hemorrhage. Fluorescein angiography in the RE revealed a hyperfluorescent structure emanating from the superotemporal arcade of the artery compatible with a macroaneurysm. The patient was treated with three intravitreal antivascular endothelial growth factor injections with poor visual outcomes. Vision loss occurs with RAM complications. They mainly involve hemorrhages and macular exudations and are usually associated with poor visual recovery. There is no established treatment for RAM and its complications. There are many options, but the optimal therapy is still unknown.

Complex organosulfur molecules on comet 67P: Evidence from the ROSINA measurements and insights from laboratory simulations.

The ROSINA (Rosetta Orbiter Spectrometer for Ion and Neutral Analysis) instrument aboard the Rosetta mission revolutionized our understanding of cometary material composition. One of Rosetta's key findings is the complexity of the composition of comet 67P/Churyumov-Gerasimenko. Here, we used ROSINA data to analyze dust particles that were volatilized during a dust event in September 2016 and report the detection of large organosulfur species and an increase in the abundances of sulfurous species previously detected in the coma. Our data support the presence of complex sulfur-bearing organics on the surface of the comet. In addition, we conducted laboratory simulations that show that this material may have formed from chemical reactions that were initiated by the irradiation of mixed ices containing H2S. Our findings highlight the importance of sulfur chemistry in cometary and precometary materials and the possibility of characterizing organosulfur materials in other comets and small icy bodies using the James Webb Space Telescope.

Efficacy of a premedication with melatonin during cataract surgery under peribulbar block: a prospective randomized double-blinded study.

INTRODUCTION: Cataract is a ubiquitous pathology. Its prevalence increases with age. Nowadays, cataract surgery is increasingly performed on an outpatient basis under locoregional anesthesia. In this context, sedation-analgesia is essential but not without risks. AIM: To evaluate the effectiveness of premedication with melatonin on intraoperative sedation-analgesia. METHODS: This is a prospective randomized double-blind study including patients proposed for scheduled cataract surgery by phacoemulsification under peribulbar anesthetic block. The participants will be randomized into two groups: group (M) will receive 05 tablets of melatonin (10mg sublingual) and group (P) will receive 05 tablets of Sucralose sublingually. Perioperative sedation-analgesia will be evaluated by the Ramsey score, the bisectral index, the simple verbal scale (EVS) and by the perioperative consumption of midazolam and alfentanyl. Secondary endpoints will be the degree of preoperative anxiety (Amsterdam Preoperative, Anxiety and Information Scale), the perioperative tonus of the eyeball, intraoperative nicardepine consumption and patients and surgeons satisfaction. A value of p <0.05 will be considered statistically significant. EXPECTED RESULTS: The administration of melatonin as a premedication for scheduled cataract surgery will allow a better quality of intraoperative sedationanalgesia, a reduction in the doses consumed of midazolam and alfentanyl, improves surgical conditions, leads to a decrease in ocular tone, and optimizes surgical safety conditions for the patient.

Postcoital visual loss due to valsalva retinopathy: A case report.

Valsalva retinopathy is a rare pathology presenting as a sudden and painless loss of vision affecting young subjects with no medical history. It is the result of an increase of intraocular venous pressure, leading to retrohyaloid haemorrhage. We describe here the clinical presentation of a retrohyaloid hemorrhage resulting from a valsalva mechanism following a sexual activity, in a 28-year-old patient treated by Neodymium:yttrium-aluminum-garnet (Nd:YAG) laser hyaloidotomy with a visual recovery of 20/20 on 3 weeks follow-up. Valsalva retinopathy is a rare and an easy-to-diagnose pathology that is safely handled by Nd:YAG laser hyaloidotomy for a quick visual acuity recovery.

Sterile endophthalmitis after intravitreal triamcinolone acetonide injection: A case report series.

Corticosteroids have proven their effectiveness in the treatment of cystoid macular edema. Especially after an intravitreal injection. Triamcinolone acetonide is the most commonly used in the treatment of macular edema. Noninfectious endophthalmitis is a form of endophthalmitis that can occur in the absence of a defined germ after an intravitreal injection of triamcinolone acetonide. We report here the case of three diabetic patients, who presented with visual blur, three days after an intra vitreal triamcinolone acetonide injection performed in the right eye. The vitreous inflammation resolved spontaneously in the first two cases after three weeks, and after four weeks for the third. The diagnosis of sterile endophthalmitis was made in view of the spontaneous resolution of the inflammation without the use of intravitreal injection of antibiotics and/or vitreoretinal surgery.

A challenging case of an intraorbital foreign body in a child: A case report.

Apart from congenital causes, orbital trauma is a leading cause of unilateral vision loss in children. We report the case of a 2-year-old child who was victim of an orbital trauma of the right eye caused by a ballpoint pen. He consulted us the day after the trauma with significant palpebral edema making the examination difficult. An emergency CT scan of the orbit and brain showed the presence of a right intraorbital foreign body. The patient underwent removal of the foreign body by an anterior orbitotomy with general antibiotic therapy and a simple postoperative course. Penetrating trauma to the orbit should raise the suspicion of the presence of a foreign body. A CT scan should be performed to specify its location. The extraction of the foreign body can be a challenge that requires an experienced surgical team.

Kyrieleis arteritis associated with toxoplasmic retinochoroiditis: A case report.

-Kyrieleis arteritis is a rare manifestation in posterior uveitis-Kyrieleis arteritis is most frequently reported in ocular toxoplasmosis.-The pathogenesis still highly debated.-It is characterized by the presence of focal, segmental plaques or exudates within retinal arteries.-These plaques are usually reversible.-The prognosis is usually good.

Acute posterior multifocal placoid pigment epitheliopathy associated with serous retinal detachment: A case report.

We report the occurrence of serous retinal detachment (SRD) in acute posterior multifocal placoid pigment epitheliopathy (APMPPE). A 22-year-old man with no general or ophthalmological pathological history presented with an acute and bilateral decreased visual acuity. There was no notion of recent flu or recent vaccination. There were anterior chamber cells and vitreous cells. Fundus revealed white-yellowish lesions, scattered on posterior pole and periphery, associated with SRD in both eyes. Fluorescein Angiography showed early hypofluorescence followed by late hyperfuorescence. Optical coherence tomography (OCT) showed hyperreflective bands of the outer nuclear layer and interruption of the ellipsoid zone associated with bilateral SRD. Repeat OCT revealed a spontaneous and complete regression of SRD in both eyes, and improvement of visual acuity after one week of evolution without any treatment. Serous retinal detachment is an uncommon manifestation of APMPPE. It is more suggestive of Vogt-Koyanagi-Harada disease (VKH), although angiographic features are typically observed in APMPPE. Moreover, spontaneous decrease of SRD within a few days is more in favor of APMPPE.

White-centered retinal hemorrhage revealing acute leukemia: A case report.

Retinal manifestations have been described as an inaugural manifestation of acute leukemia. Retinal hemorrhage, and in particular white-centered hemorrhages are among the most frequently observed signs. We report here the case of a 34-year-old Caucasian man with no medical history who presented to our emergency department with a decrease in visual acuity associated with asthenia. Ophthalmological examination revealed bilateral white-centered hemorrhages. The etiological assessment confirmed the diagnosis of acute myeloid leukemia. Whenever Roth spots are found in fundus examination, a complete ophthalmological examination along with a wide etiological investigation must be conducted.

Behçet's disease presenting as neuroretinitis with pre-papillary vitreous infiltrate: a case report.

OBJECTIVE: To report a case of Behçet's disease (BD) presenting as a panuveitis with neuroretinitis and pre-papillary vitreous infiltrate. MATERIAL AND METHODS: A case report. RESULTS: A 43-year-old male presented with severely decreased vision in the left eye. Ophthalmological examination revealed unilateral non granulomatous panuveitis with occlusive retinal vasculitis, neuroretinitis and pre-papillary vitreous infiltrate. Initial swept source OCT revealed a "funnel-shaped" hyperreflective lesion overlying the optic disc corresponding to the pre-papillary vitreous infiltrate associated with optic disc edema and a serous retinal detachment extending to the macula. Examination by an internal medicine specialist revealed buccal aphthous ulcer and pseudofolliculitis lesions. BD diagnosis was made and the patient received corticosteroid and immunosuppressive therapy. The pre-papillary vitreous infiltrate resolution under treatment was documented with repeat swept source OCT. CONCLUSION: Pre-papillary vitreous infiltrate has been rarely reported in the literature. This finding is a typical feature in severe cases of BD uveitis and is usually associated with a neuroretinitis. Optic disc OCT is useful to make the diagnosis and to monitor the resolution of the pre-papillary vitreous infiltrate.

Slow photoelectron spectroscopy of δ-valerolactam and its dimer.

We studied the single-photon ionization of gas-phase δ-valerolactam (piperidin-2-one) and of its dimer using vacuum-ultraviolet (VUV) synchrotron radiation coupled to a velocity map imaging electron/ion coincidence spectrometer. The slow photoelectron spectrum (SPES) of the monomer is dominated by the vibrational transitions to the ͠X state. Moreover, several weaker and complex bands are observed, corresponding to the population of the vibrational bands (pure or combination) of the electronically excited states of the cation arising from their mutual vibronic interactions. For the dimer, we measure a unique large band. These spectra are assigned with the help of theoretical calculations dealing with the equilibrium geometries, electronic-state patterns and evolutions, harmonic and anharmonic wavenumbers of the monomer and dimer, either neutral or positively charged. The state energies of the [δ-valerolactam](+) cation in the ͠X ground, ͠A, ͠B, ͠C, excited electronic states, and of the [δ-valerolactam](2) (+) cation's lowest states are determined. After its formation, [δ-valerolactam](2) (+) is subject to intramolecular isomerization, H transfer and then unimolecular fragmentation processes. Close to the ionization thresholds, the photoionization of these molecules is found to be mainly dominated by a direct process whereas the indirect route (autoionization) contributes at higher energies.

Role of conformational isomerism in solvent-mediated charge transfer in chiral (S) 1,2,3,4-tetrahydro-3-isoquinoline methanol (THIQM): condensed-phase to jet-cooled spectroscopic studies.

Intramolecular charge-transfer reaction in chiral (S) 1,2,3,4-tetrahydro-3-isoquinoline methanol (THIQM) has been investigated in the condensed phase and in jet-cooled conditions by means of laser-induced fluorescence, dispersed emission, resonance-enhanced two-photon ionization, and IR-UV double resonance experiments, as well as quantum chemical calculations. In the condensed phase, THIQM only shows local emission in nonpolar and protic solvents and dual emission in aprotic polar solvents, where the solvent-polarity dependent Stokes shifted emission is ascribed to a state involving charge transfer from the nitrogen lone pair to the benzene π-cloud. Ab initio calculations reveal two low-energy conformers, which are observed in jet-cooled conditions. In the most stable conformer, THIQM(I), the CH(2)OH substituent acts as a hydrogen bond donor to the nitrogen lone pair in the equatorial position, while the second most stable conformer, THIQM(II), corresponds to the opposite NH···O hydrogen bond, with the nitrogen lone pair in the axial position. The two low-energy jet-cooled conformers of THIQM evidenced from the laser-induced fluorescence and dispersed emission spectra only show structured local emission. Complexes with usual solvents reproduce the condensed phase properties. The jet-cooled complex with aprotic polar solvent acetonitrile shows both local emission and charge transfer emission as observed in solution. The jet-cooled hydrate mainly shows local emission due to the unavailability of the nitrogen lone pair through intermolecular hydrogen bonding.

Contribution of optical coherence tomography angiography OCT-A in diabetic maculopathy.

INTRODUCTION: Diabetic retinopathy (DR) increases the risk of blindness by 25 times. Advanced researchs are justified for better management, leading to the role of Optical Coherence Tomography-Angiography (OCT-A), a new non-invasive imaging technique exploring retinal vascularization.Our purpose is to identify microvascular macular anomalies of DR on OCT-A with qualitative and quantitative evaluation of their impact on retinal vascularization. PATIENTS AND METHODS: This is a descriptive cross-sectional study where 120 eyes of 66 diabetic patients were enrolled. All patients were diabetic and went through OCT-A imaging. RESULTS: Microanevrysms were identified in both superficial capillary plexus (SCP) and deep capillary plexus (DCP) where they were more frequently visualized. Macular edema was present in 16,7% of cases in the SCP, and in 30% in DCP. Edema spaces were more frequently present in DCP (p < 0,05). Capillary nonperfusion areas were identified in 82,5% of cases in SCP and in 60% of cases in DCP. The main peri-foveal vascular density was 18,95 ± 5,37%. The main surface of foveal avascular zone (FAZ) in the SCP was 462,52 µm2 and was 555,04 ± 329,11 µm2 in the DCP where it was larger. CONCLUSION: OCT-A is a modern imaging tool that could be used for the diagnosis and monitoring of DR as well as the understanding of its pathophysiology.

Optic nerve avulsion: Case report.

INTRODUCTION: Optic nerve avulsion is a traumatic disinsertion of optic nerve fibres from the globe at the level of the lamina cribrosa. It is an uncommon and severe complication of blunt ocular trauma. CASE PRESENTATION: We report the case of a 15 years old male presented to the emergency department after being kicked by a horse. Initial ophthalmologic examination of the left eye (LE), exhibited eyelid hematoma, subconjunctival hemorrhage, VA was limited to light perception and there was a left relative afferent pupillary defect. Dilated fundus examination of the LE revealed an extensive vitreous and preretinal hemorrhage overlaying the optic disc and retina edema.The diagnosis of LE optic nerve head avulsion (ONA) was made. Five years after the accident, VA of LE detecting hand motion, fundus examination revealed a superior dragging of the optic disc, fibroglial scarring, retinal vessel narrowing and retinal epithelium hyperplasia. CLINICAL DISCUSSION: In case of ONA, the avulsion can be missed initially due to vitreous and retinal hemorrhage overlaying the optic nerve, in such cases multimodal imaging can be a useful tool to the diagnosis and to evaluate associated ocular damage. Healing process of the avulsed optic nerve is characterized by the development of fibroglial proliferation. Visual outcome is poor and the final visual acuity range from light perception or no light perception in total ONA. CONCLUSION: Optic head nerve avulsion is a rare and severe disease and initial diagnosis is challenging due to associated media opacities. The prognosis is poor and the injury leads to permanent visual impairment.

Retinal vein occlusions: an OCT- Angiography analysis.

AIM: To analyze microcirculatory abnormalities, central avascular area and capillary density in OCT-angiography in retinal venous occlusions (RVO). METHODS: This is a descriptive study of 35 patients (35 eyes) with RVO who consulted at the  ophthalmology department of Farhat Hached Hospital in Sousse between January 2014 and July 2018. The diagnosis of retinal venous occlusion was established on clinical examination, fundus photography and fluorescein angiography. All patients underwent OCT-angiography and OCT B-scan. RESULTS: Our study includes a total of 35 patients (35 eyes). Of these patients, 20 (57.1%) had branch retinal vein occlusion and 15 (42.8%) had central retinal vein occlusion. The loss or rarefaction of the capillary plexus concerned the deep capillary plexus (DCP) more than the superficial one (SCP). This rarefaction was observed in 25 eyes (71.42%) in both DCP and SCP. The widening of the central avascular zone and the rupture of the peri-foveolar anastomotic mesh were better or as visible as fluorescein angiography. Vascular tortuosity was easy to analyze and was more evident in the SCP than the DCP. Twenty-six (74.28%) patients had vascular tortuosity in DCP and 30 patients (85.71%) had this vascular tortuosity in SCP. Capillary dilatation and microaneurysms were better visible in the DCP than the SCP. These vascular abnormalities were found in 26 cases (74.28%) in the DCP and in 17 cases (48.57%) in the SCP. CONCLUSIONS: OCT-A is a non-invasive examination that allows very precise analysis and follow-up of both macular edema and superficial and deep capillary plexus architecture during retinal vein occlusions.