Widespread detection of chlorine oxyacids in the Arctic atmosphere

Chlorine radicals are strong atmospheric oxidants known to play an important role in the depletion of surface ozone and the degradation of methane in the Arctic troposphere. Initial oxidation processes of chlorine produce chlorine oxides, and it has been speculated that the final oxidation steps lead to the formation of chloric (HClO₃) and perchloric (HClO₄) acids, although these two species have not been detected in the atmosphere. Here, we present atmospheric observations of gas-phase HClO₃ and HClO₄. Significant levels of HClO₃ were observed during springtime at Greenland (Villum Research Station), Ny-Ålesund research station and over the central Arctic Ocean, on-board research vessel Polarstern during the Multidisciplinary drifting Observatory for the Study of the Arctic Climate (MOSAiC) campaign, with estimated concentrations up to 7 × 10⁶ molecule cm^-3. The increase in HClO₃, concomitantly with that in HClO₄, was linked to the increase in bromine levels. These observations indicated that bromine chemistry enhances the formation of OClO, which is subsequently oxidized into HClO₃ and HClO₄ by hydroxyl radicals. HClO₃ and HClO₄ are not photoactive and therefore their loss through heterogeneous uptake on aerosol and snow surfaces can function as a previously missing atmospheric sink for reactive chlorine, thereby reducing the chlorine-driven oxidation capacity in the Arctic boundary layer. Our study reveals additional chlorine species in the atmosphere, providing further insights into atmospheric chlorine cycling in the polar environment.

Why airborne transmission hasn't been conclusive in case of COVID-19? An atmospheric science perspective

Airborne transmission is one of the routes for the spread of COVID-19 which is caused by inhalation of smaller droplets1 containing SARS-CoV-2 (i.e., either virus-laden particulate matter: PM and/or droplet nuclei) in an indoor environment. Notably, a significant fraction of the small droplets, along with respiratory droplets, is produced by both symptomatic and asymptomatic individuals during expiratory events such as breathing, sneezing, coughing and speaking. When these small droplets are exposed to the ambient environment, they may interact with PM and may remain suspended in the atmosphere even for several hours. Therefore, it is important to know the fate of these droplets and processes (e.g., physical and chemical) in the atmosphere to better understand airborne transmission. Therefore, we reviewed existing literature focussed on the transmission of SARS-CoV-2 in the spread of COVID-19 and present an environmental perspective on why airborne transmission hasn't been very conclusive so far. In addition, we discuss various environmental factors (e.g., temperature, humidity, etc.) and sampling difficulties, which affect the conclusions of the studies focussed on airborne transmission. One of the reasons for reduced emphasis on airborne transmission could be that the smaller droplets have less number of viruses as compared to larger droplets. Further, smaller droplets can evaporate faster, exposing SARS-CoV-2 within the small droplets to the environment, whose viability may further reduce. For example, these small droplets containing SARS-CoV-2 might also physically combine with or attach to pre-existing PM so that their behaviour and fate may be governed by PM composition. Thus, the measurement of their infectivity and viability is highly uncertain due to a lack of robust sampling system to separately collect virions in the atmosphere. We believe that the present review will help to minimize the gap in our understanding of the current pandemic and develop a robust epidemiological method for mortality assessment.

Role of iodine oxoacids in atmospheric aerosol nucleation

Iodic acid (HIO3) is known to form aerosol particles in coastal marine regions, but predicted nucleation and growth rates are lacking. Using the CERN CLOUD (Cosmics Leaving Outdoor Droplets) chamber, we find that the nucleation rates of HIO3 particles are rapid, even exceeding sulfuric acid-ammonia rates under similar conditions. We also find that ion-induced nucleation involves IO3 - and the sequential addition of HIO3 and that it proceeds at the kinetic limit below +10°C. In contrast, neutral nucleation involves the repeated sequential addition of iodous acid (HIO2) followed by HIO3, showing that HIO2 plays a key stabilizing role. Freshly formed particles are composed almost entirely of HIO3, which drives rapid particle growth at the kinetic limit. Our measurements indicate that iodine oxoacid particle formation can compete with sulfuric acid in pristine regions of the atmosphere.

Influence of gaseous and particulate species on neutralization processes of polar aerosol and snow - A case study from Ny-Ålesund

The inter-conversion of nitrogen and sulfur species between the gas and particulate phases and their interaction with alkaline species influences the acidity of the aerosols and surface snow. To better understand these processes, a short field campaign was undertaken in Ny-Ålesund, Svalbard, during 13th April 2012 to 24th April 2012. Air measurements were carried out through a particulate sampler equipped with denuders and filter packs for simultaneous collection of trace gases (HNO₃, NO₂, SO₂ and reactive nitrogen compounds) and aerosols, with daily collection of snow samples. Ionic composition of the samples was analyzed using ion chromatography technique. The results suggested that nitrate-rich aerosols are formed when PAN (peroxy acetyl nitrate) disassociates to form NO₂ and HNO₃ which further hydrolyzes to form pNO₃^- (particulate nitrate). This resulted in a high contribution of pNO₃^- (62%) to the total nitrogen budget over the study area. The acidity of the aerosols and snow evaluated through cation/anion ratio (C/A) indicated alkaline conditions with C/A>2. The bicarbonates/carbonates of Mg²⁺ played an important role in neutralization processes of surface snow while the role of NH₃ was dominant in aerosol neutralization processes. Such neutralization processes can increase the aerosol hygroscopicity causing warming. Chloride depletion in the snow was significant as compared to the aerosols, indicating two important processes, scavenging of coarse sea salt by the snow and gaseous adsorption of SO₂ on the snow surface. However, a more systematic and long term study is required for a better understanding of the neutralization processes and chemical inter-conversions.

Intradural Eosinophilic Granuloma Invading Skull: Case Report and Review of the Literature

Eosinophilic granuloma is a localized form of Langerhans cell histiocytosis, most commonly involving the skeletal system. Their origin from the dura is rare with only a handful of cases on record. We present one such rare case of an eosinophilic granuloma originating from the dura mater with secondary osseous invasion in an 11-year-old female child who presented with a swelling in the right parietal region. Magnetic resonance imaging demonstrated an enhancing mass with a wide dural attachment with a lytic lesion in the overlying skull. Right parietal extended craniotomy was done with the excision of mass from the dura. Histopathological features of mass were characteristic of eosinophilic granuloma which was confirmed by positive immunohistochemical staining for CD1a.

Ganglioneuroma arising from the L5 nerve root: A rare case report

Ganglioneuroma is a rare, benign, slow-growing, well-differentiated tumor consisting ganglion cells and Schwann cells. Ganglioneuromas originate from neural crest cells and can affect any part of the sympathetic tissue from the skull base to the pelvis. However, ganglioneuroma occurring in the nerve root is extremely rare. We describe a 44-year-old man with ganglioneuroma involving the right fifth lumbar nerve root.

Rhabdoid meningioma lacking malignant features: Report of a rare case with review of literature

We reported a case of meningioma with rhabdoid morphology but lacking histological features of malignancy in arising from the spinal cord in a 28-year-old male. The tumor showed light microscopic, immunohistochemical evidence of meningothelial differentiation together with diffuse areas exhibiting rhabdoid morphology. The rhabdoid areas were characterized by cells with large cytoplasmic eosinophilic inclusions and eccentric nuclei. Unlike most cases reported in the literature, this case lacked significant mitotic activity and other atypical features. The diagnostic and prognostic significance of this tumor entity is discussed along with a review of the literature.

Trace metal concentrations of surface snow from Ingrid Christensen Coast, East Antarctica--spatial variability and possible anthropogenic contributions

To investigate the distribution and source pathways of environmentally critical trace metals in coastal Antarctica, trace elemental concentrations were analyzed in 36 surface snow samples along a coast to inland transect in the Ingrid Christensen Coast of East Antarctica. The samples were collected and analyzed using the clean protocols and an inductively coupled plasma mass spectrometer. Within the coastal ice-free and ice-covered region, marine elements (Na, Ca, Mg, K, Li, and Sr) revealed enhanced concentrations as compared with inland sites. Along with the sea-salt elements, the coastal ice-free sites were also characterized by enhanced concentrations of Al, Fe, Mn, V, Cr, and Zn. The crustal enrichment factors (Efc) confirm a dominant crustal source for Fe and Al and a significant source for Cr, V, Co, and Ba, which clearly reflects the influence of petrological characteristics of the Larsemann Hills on the trace elemental composition of surface snow. The Efc of elements revealed that Zn, Cu, Mo, Cd, As, Se, Sb, and Pb are highly enriched compared with the known natural sources, suggesting an anthropogenic origin for these elements. Evaluation of the contributions to surface snow from the different sources suggests that while contribution from natural sources is relatively significant, local contamination from the increasing research station and logistic activities within the proximity of study area cannot be ignored.

Micropropagation and germplasm conservation of Central Park Splendor Chinese elm (Ulmus parvifolia Jacq. 'A/Ross Central Park') trees

Micropropagation offers opportunities to propagate, preserve and ship tree germplasm. It also reduces the risk of moving pathogens and insects with the germplasm due to built-in pathogen detection capabilities of aseptic cultures. For the past few decades, our laboratory has been involved in a project to preserve and restore a large, cold hardy, and historically important Chinese elm (Ulmus parvifolia Jacq. 'A/Ross Central Park') tree. Here we present three simple and efficient systems for its micropropagation, germplasm conservation and distribution: (1) in vitro plant formation from meristematic nodules (MNs), (2) plantlet generation from axillary buds, and (3) in vitro rooting of micro-cuttings from 20-years-old hedged stock plants. Newly flushed nodal segments were used as explants. WPM with 0.5 mg/l BA was found to be the best medium for meristematic shoot development and WPM supplemented with 2.0 mg/l 4-CPPU and 0.5 mg/l TDZ was best for meristematic nodule formation. Rhizogenesis of regenerants and micro-cuttings was best achieved on WPM with 1.0 mg/l NAA and 2% sucrose. Rooted plants were readily acclimatized to the greenhouse ambient environment and continued to grow well under greenhouse conditions. The survival rate of acclimatized plantlets under ex vitro conditions was 100% after 4 weeks. Plants looked healthy with no visually detectable phenotypic variation based on observation of about 1,000 plants. Cycling of shoot explants and MNs through repetitive cultures was effective in scaling-up propagules.

Rapid in vitro propagation of Matteuccia struthiopteris (L.) Todaro - an edible fern

A rapid and efficient in vitro plant regeneration method was developed for Matteuccia struthiopteris (L.) Todaro (Ostrich fern). Side shoots, originating in meristems of sectioned rhizomes, were used as explant material. A very high rate of meristem multiplication was achieved by culturing the explants in half-strength MS liquid medium supplemented with 2.0 mg/l N-(4-Pyridyl)-N'-phenylurea (4-PU) and 0.5 mg/l thidiazuron (TDZ). Multiplication of the shoot primordia was faster in suspension culture than on solid medium. Rhizogenesis and growth of regenerants were best achieved on hormone-free one-quarter-strength MS solid medium amended with 0.4% agar and 1.0% activated charcoal. Regenerated plantlets continued to grow after transfer to soil in a phytotron.

Large exophytic chondrosarcoma of cervicodorsal spine without spinal cord compression : a case report with review of literature

A case of well differentiated chondrosarcoma arising from the laminae and spinous processes of cervicodorsal spine is reported in a 22-years-old patient. He had presented with a painless progressive mass in the cervicodorsal region, without any neurological deficit. The tumour had a large exophytic growth without any intraspinal component. Radiological appearance of cartilaginous calcification suggested the diagnosis of a cartilaginous tumour. Fine needle aspiration cytology (FNAC) from the mass failed to differentiate between a chondroma and a well differentiated chondrosarcoma. The final histopathological diagnosis of the surgically excised tumour was possible only after a detailed radiological and clinicopathological correlation. Total surgicalexcision of the tumour was followed by radiation therapy. A review of literature is included in view of the rarity of this condition and scarcity of similar reports in the Indian literature.

Craniospinal intradural arachnoid cyst

A patient with an uncommonly situated congenital intradural arachnoid cyst is reported. The cyst extended from the cervical spinal canal into the posterior cranial fossa and was posterolateral to the spinal cord. The patient's initial complaint was urinary hesitancy. The location of the cyst is unique and the presenting complaint rare.

Intramedullary spinal cord abscess: a case report

An 11-year-old boy presented with pain in the back, urinary retention, paraplegia and loss of sensations below L1. Investigations revealed an intramedullary lesion. An intramedullary spinal cord abscess was found at surgery. The pus was evacuated and abscess was excised. Minimal recovery was seen following surgery. Early intervention and a high index of suspicion is required in such cases.

Air in epidural haematomas

Air in epidural haematoma is an uncommon finding. It is usually seen if epidural haematoma is associated with fracture involving one of the air sinuses, but can be seen at times in the absence of any demonstrable fracture on the CT scan. Seven such cases are described in the present communication and the significance of this finding discussed.

Non-missile penetrating injuries of the spine

Non-missile penetrating injuries of the spine accounted for 7% of all spinal injuries admitted to this Institute during the last 10 years. Young males were most commonly affected and 73% of the injuries involved the upper dorsal und cervical spine. They presented with varying degrees of neurological deficit. Plains x-rays revealed the bony injury and/or the retained foreign body satisfactorily. Myelography (with or without CT scan) was performed in patients with progressive neurological deterioration and those not responding to conservative therapy. Surgery remained the mainstay of treatment and improved neurological function in 7 out of 9 cases. Conservative management resulted in complications such as persistent CSF fistula, uncontrolled fulminant meningitis and septicaemia, with 100% mortality. Early surgical intervention is, therefore, recommended in all penetrating injuries of the spine.

Spinal subarachnoid haematoma after stab injury of the cauda equina

An unusual case of an anterior stab injury, involving the cauda equina, with a progressive neurological deterioration is presented. Myelography showed a filling defect and surgery revealed a subarachnoid clot. Good recovery followed removal of the clot.