Cohort profile: The Clinical and Multi-omic (CAMO) cohort, part of the Norwegian Women and Cancer (NOWAC) study

INTRODUCTION

Breast cancer is the most common cancer worldwide and the leading cause of cancer related deaths among women. The high incidence and mortality of breast cancer calls for improved prevention, diagnostics, and treatment, including identification of new prognostic and predictive biomarkers for use in precision medicine.

MATERIAL AND METHODS

With the aim of compiling a cohort amenable to integrative study designs, we collected detailed epidemiological and clinical data, blood samples, and tumor tissue from a subset of participants from the prospective, population-based Norwegian Women and Cancer (NOWAC) study. These study participants were diagnosed with invasive breast cancer in North Norway before 2013 according to the Cancer Registry of Norway and constitute the Clinical and Multi-omic (CAMO) cohort. Prospectively collected questionnaire data on lifestyle and reproductive factors and blood samples were extracted from the NOWAC study, clinical and histopathological data were manually curated from medical records, and archived tumor tissue collected.

RESULTS

The lifestyle and reproductive characteristics of the study participants in the CAMO cohort (n = 388) were largely similar to those of the breast cancer patients in NOWAC (n = 10 356). The majority of the cancers in the CAMO cohort were tumor grade 2 and of the luminal A subtype. Approx. 80% were estrogen receptor positive, 13% were HER2 positive, and 12% were triple negative breast cancers. Lymph node metastases were present in 31% at diagnosis. The epidemiological dataset in the CAMO cohort is complemented by mRNA, miRNA, and metabolomics analyses in plasma, as well as miRNA profiling in tumor tissue. Additionally, histological analyses at the level of proteins and miRNAs in tumor tissue are currently ongoing.

CONCLUSION

The CAMO cohort provides data suitable for epidemiological, clinical, molecular, and multi-omics investigations, thereby enabling a systems epidemiology approach to translational breast cancer research.

POS0246 SEQUENTIAL RITUXIMAB AND MEPOLIZUMAB IN EOSINOPHILIC GRANULOMATOSIS WITH POLYANGIITIS

Background

Rituximab (RTX) is an effective remission-induction treatment in ANCA-associated vasculitides (AAVs). Some reports have suggested that it might be effective also in Eosinophilic Granulomatosis with Polyangiitis (EGPA), to induce and maintain remission of vasculitic manifestations [1,2]. However, its effects for preventing respiratory relapses seem to be poor. Mepolizumab (Mepo) (both 100 and 300mg/month) is effective in improving respiratory manifestations and lung function, while partially controlling also systemic activity [3,4]. Isolated case reports further indicate that the sequential therapy with RTX and Mepo might be effective [5-7].

Objectives

The study aimed to investigate the efficacy and safety of a therapeutic regimen based on sequential RTX and Mepo for the control of EGPA.

Methods

A multicenter, retrospective, cohort study was conducted on adult patients diagnosed with EGPA according to the ACR classification criteria [8] or MIRRA trial criteria [3]. Only patients who received induction therapy with RTX (any dosage), and subsequent treatment with Mepo (100-300 mg/4 weeks) within 12 months from last RTX administration were included. Patients receiving other induction therapies between RTX and Mepo were excluded. The effectiveness of sequential RTX and Mepo was assessed in terms of disease activity (by the Birmingham Vasculitis Activity Score, BVAS) and daily corticosteroid dosage. Safety data were also collected.

Results

Thirty-four EGPA patients treated with sequential RTX and Mepo were included (59% females, median age of 51 years (IQR 40-58); 41% ANCA positive).

In most cases (26/34; 76%), RTX was started at the dosage of 1g q2w, and all except two patients had active disease at time of RTX beginning [median BVAS of 9 (IQR 6-14)]. Specifically, most patients started RTX for the control of systemic manifestations (19/34; 56%), or of both systemic and respiratory symptoms (11/34; 32%). All except one patient were receiving oral corticosteroids, at a median dosage of 25 mg/day (10-38).

Mepo was started after a median of 14 months (6-23) from RTX initiation and after a median of 5 months (IQR 3-11) from the last RTX administration. Mepo was used at the dosage of 100mg/4 weeks in 32/34 (94%), mostly for the control of respiratory manifestations (25/34, 74%). At the time of starting Mepo, the median BVAS was 4 (2-8), and median prednisolone dose 10 mg/day (7-15). After a median follow-up of 28 months (IQR 23-33) from starting Mepo, the median BVAS decreased to 1.5 (IQR 0-4) and the median corticosteroid dosage to 5 mg/day (2.5-5), with 7/34 (21%) patients being off steroids. At last follow-up, most patients were off-RTX (28/34), typically due to stable disease remission (20/34; 59%).

Both RTX and Mepo were well-tolerated; 5 patients had adverse events on RTX (none serious), and 5 on Mepo (including one serious infection).

Conclusion

Sequential use of RTX and Mepo seems to be effective for remission induction and maintenance in EGPA.

References

[1]Emmi, Ann Rheum Dis, 2018

[2]Teixeira, RMD Open, 2019 3. Wechsler, NEJM, 2017

[4]Bettiol, Arthritis Rheumatol, 2021

[5]Shiroshita, Respir Med Case Rep, 2018

[6]Higashitani, Mod Rheumatol Case Rep, 2021

[7]Afiari, Cureus 2020

[8]Masi, Arthritis Rheum, 1990

Table 1.

Effectiveness of sequential RTX and Mepo in the 34 patients included in the study

RTX beginningMepo beginningLast follow-upMedian time elapsed (IQR)-14 months (6-23) from RTX beginning28 months (23-33) from Mepo beginningDosage1g q2w (26/34);100mg/4 weeks (32/34)6 patients off Mepo; 28 patients off RTX375mg/m2 for 4 weeks (8/34)300mg/4 weeks (2/34)Reason for treatment beginning (manifestations)Systemic (19/34);Respiratory (25/34);-Systemic + respiratory (11/34);Systemic (4/34);Only respiratory (3/34);Remission maintenance (5/34)Other (1/34)BVAS (median, IQR)9 (6-14)4 (2-8)1.5 (0-4)Prednisolone dosage (median, IQR), mg/day25 (10-38)10 (7-15)5 (2.5-5)

Disclosure of Interests

Alessandra Bettiol: None declared, Maria Letizia Urban: None declared, Federica Bello: None declared, Davide Fiori: None declared, Irene Mattioli: None declared, Giuseppe Lopalco: None declared, Florenzo Iannone: None declared, Allyson Egan: None declared, Luca Moroni: None declared, Lorenzo Dagna Consultant of: Consultation honoraria from GSK outside the current work, Marco Caminati: None declared, Simone Negrini: None declared, Paolo Cameli: None declared, Marco Folci: None declared, Paola Toniati: None declared, Roberto Padoan: None declared, Oliver Flossmann: None declared, Roser Solans-Laqué: None declared, Laura Losappio: None declared, Jan Schroeder Consultant of: Advisory Board fees from AstraZeneca and GSK, Marc André: None declared, Laura Moi: None declared, paola parronchi Consultant of: Consultation honoraria from GSK and Novartis, Fabrizio Conti: None declared, Savino Sciascia: None declared, David Jayne Consultant of: Consultant for Astra-Zeneca, Aurinia, BMS, Boehringer-Ingelheim, Chemocentryx, Chugai, CSL, GSK, Infla-RX, Janssen, Novartis, Roche/Genentech, Takeda and Vifor, Augusto Vaglio Consultant of: Consultation honoraria from GSK outside the current work, Giacomo Emmi Consultant of: Consultation honoraria from GSK outside the current work

Serglycin Is Involved in TGF-β Induced Epithelial-Mesenchymal Transition and Is Highly Expressed by Immune Cells in Breast Cancer Tissue

Serglycin is a proteoglycan highly expressed by immune cells, in which its functions are linked to storage, secretion, transport, and protection of chemokines, proteases, histamine, growth factors, and other bioactive molecules. In recent years, it has been demonstrated that serglycin is also expressed by several other cell types, such as endothelial cells, muscle cells, and multiple types of cancer cells. Here, we show that serglycin expression is upregulated in transforming growth factor beta (TGF-β) induced epithelial-mesenchymal transition (EMT). Functional studies provide evidence that serglycin plays an important role in the regulation of the transition between the epithelial and mesenchymal phenotypes, and it is a significant EMT marker gene. We further find that serglycin is more expressed by breast cancer cell lines with a mesenchymal phenotype as well as the basal-like subtype of breast cancers. By examining immune staining and single cell sequencing data of breast cancer tissue, we show that serglycin is highly expressed by infiltrating immune cells in breast tumor tissue.

A man in his sixties with dyspnoea and oedema

BACKGROUND/CASE PRESENTATION

A man in his sixties with chronic obstructive pulmonary disease was hospitalised due to oedema and dyspnoea during the previous weeks. He was hypertensive, with 10 kg weight gain, generalised oedema, proximal myopathy and moon face. The assessment was consistent with ectopic ACTH-dependent Cushing's syndrome. A 15 mm lung tumour was detected on CT, with inconclusive cytological examination, and negative FDG/PET CT and octreotide scintigraphy. He developed necrotising pancreatitis and a duodenal perforation, which were surgically treated. His cortisol levels and Cushingoid appearance normalised after surgery, and it was concluded that his hypercortisolism was part of a physiological response. He remained clinically in habitual shape until two years later, when he again developed Cushingoid stigmata. A new octreotide scintigraphy was negative, but FDG/PET CT revealed increased FDG uptake in the lung lesion. Before a lung biopsy was performed, the patient developed necrotising pancreatitis. He was treated conservatively and died in respiratory failure. Autopsy revealed a NET in the lung and necrotising pancreatitis.

INTERPRETATION

The case demonstrates diagnostic challenges in the assessment of ectopic ACTH-dependent cyclic Cushing's syndrome. Is also suggests that pancreatitis could be triggered by hypercortisolism.

Differential expression of the miR-17-92 cluster and miR-17 family in breast cancer according to tumor type; results from the Norwegian Women and Cancer (NOWAC) study

Background

MicroRNAs (miRNAs) are promising biomarkers due to their structural stability and distinct expression profile in various cancers. We wanted to explore the miRNA expression in benign breast tissue and breast cancer subgroups in the Norwegian Women and Cancer study.

Methods

Specimens and histopathological data from study participants in Northern Norway diagnosed with breast cancer, and benign tissue from breast reduction surgery were collected. Main molecular subtypes were based on surrogate markers; luminal A (ER+ and/or PR+, HER2− and Ki67 ≤ 30%), luminal B (ER+ and/or PR+, HER2− and Ki67 > 30% or ER+ and/or PR+ and HER2+), HER2 positive (ER− and PR− and HER2+) and triple-negative (ER−, PR− and HER2−). RNA was extracted from formalin-fixed paraffin-embedded (FFPE) tissue, and miRNAs were successfully analyzed in 102 cancers and 36 benign controls using the 7th generation miRCURY LNA microarray containing probes targeting all human miRNAs as annotated in miRBASE version 19.0. Validation with RT-qPCR was performed.

Results

On average, 450 miRNAs were detected in each sample, and 304 miRNAs were significantly different between malignant and benign tissue. Subgroup analyses of cancer cases revealed 23 miRNAs significantly different between ER+ and ER− tumors, and 47 miRNAs different between tumors stratified according to grade. Significantly higher levels were found in high grade tumors for miR-17-5p (p = 0.006), miR-20a-5p (p = 0.007), miR-106b-5p (p = 0.007), miR-93-5p (p = 0.007) and miR-25-3p (p = 0.015) from the paralogous clusters miR-17-92 and miR-106b-25. Expression of miR-17-5p (p = 0.0029), miR-20a-5p (p = 0.0021), miR-92a-3p (p = 0.011) and miR-106b-5p (p = 0.021) was significantly higher in triple-negative tumors compared to the rest, and miR-17-5p and miR-20a-5p were significantly lower in luminal A tumors.

Conclusions

miRNA expression profiles were significantly different between malignant and benign tissue and between cancer subgroups according to ER− status, grade and molecular subtype. miRNAs in the miR-17-92 cluster and miR-17 family were overexpressed in high grade and triple-negative tumors associated with aggressive behavior. The expression and functional role of these miRNAs should be further studied in breast cancer to explore their potential as biomarkers in diagnostic pathology and clinical oncology.

Expression and function of the miR-143/145 cluster in vitro and in vivo in human breast cancer

MicroRNAs (miRNAs) are small non-coding RNAs that function as post-transcriptional regulators of gene expression and are dysregulated in cancer. Studies of miRNAs to explore their potential as diagnostic and prognostic markers are of great scientific interest. Here, we investigate the functional properties and expression of the miR-143/145 cluster in breast cancer (BC) in vitro and in vivo. The ER positive MCF7, the HER2 positive SK-BR-3, and the triple negative cell line MDA-MB-231 were used to assess cell proliferation and cell invasion. Expression of miRNA in 108 breast cancers in the Norwegian Women and Cancer Study and 44 benign tissue controls were analyzed by microarray and validated by RT-PCR. Further, in situ hybridization (ISH) was used to study the cellular and subcellular distribution of the miRNAs. In vitro, miR-143 promoted proliferation of MCF7 and MDA-MB-231 cells, whereas miR-145 and the cotransfection of both miRNAs inhibited proliferation in all three cell lines. The cells’ invasive capacity was reduced after transfection and cotransfection of the miRNAs. In line with the tumor suppressive functions in vitro, the expression of miR-143 and miR-145 was lower in malignant compared to benign breast tissue, and lower in the more aggressive tumors with higher tumor grade, loss of ER and the basal-like phenotype. ISH revealed miR-143 to be cytoplasmatic and predominantly expressed in luminal cells in benign tissue, whilst miR-145 was nuclear and with strong staining in myoepithelial cells. Both miRNAs were present in malignant epithelial cells and stromal fibroblasts in BC. This study demonstrates that miR-143 and -145 have functional properties and expression patterns typical for tumor suppressors, but the function is influenced by cellular factors such as cell type and miRNA cotransfection. Further, the nuclear functions of miR-145 should be explored for a more complete understanding of the complexity of miRNA regulation and function in BC.

Observation of 7pP23/2→7dD2 optical transitions in 209 and 210 francium isotopes

We report on the direct experimental observation of the 7pP2_3/2→7dD2 optical transitions in 209 and 210 francium isotopes. By continuously monitoring the fluorescence emitted by the isotopes collected in a magneto-optical trap (MOT), the electric dipole transitions 7pP2_3/2→7dD2_5/2 of Fr209, not yet experimentally observed, and 7pP2_3/2→7dD2_5/2, 7pP2_3/2→7dD2_5/2 of Fr210 were detected as sub-Doppler depletion dips of the cold atom population. This approach allowed unambiguous identification of the excited state hyperfine structures, even in the absence of a large stable vapor. Our findings demonstrate the effectiveness and the flexibility of fluorescence monitoring of trap depletion upon laser excitation, and broaden the experimental knowledge of francium isotopes and their electronic and nuclear properties. These results will have a relevant impact on ongoing researches for low-energy testing of fundamental symmetries with francium, from atomic parity non-conservation to the electron dipole moment.

Plasma microRNAs as biomarkers of pancreatic cancer risk in a prospective cohort study

Noninvasive biomarkers for early pancreatic ductal adenocarcinoma (PDAC) diagnosis and disease risk stratification are greatly needed. We conducted a nested case-control study within the Prospective Investigation into Cancer and Nutrition (EPIC) cohort to evaluate prediagnostic microRNAs (miRs) as biomarkers of subsequent PDAC risk. A panel of eight miRs (miR-10a, -10b, -21-3p, -21-5p, -30c, -106b, -155 and -212) based on previous evidence from our group was evaluated in 225 microscopically confirmed PDAC cases and 225 controls matched on center, sex, fasting status and age/date/time of blood collection. MiR levels in prediagnostic plasma samples were determined by quantitative RT-PCR. Logistic regression was used to model levels and PDAC risk, adjusting for covariates and to estimate area under the receiver operating characteristic curves (AUC). Plasma miR-10b, -21-5p, -30c and -106b levels were significantly higher in cases diagnosed within 2 years of blood collection compared to matched controls (all p-values <0.04). Based on adjusted logistic regression models, levels for six miRs (miR-10a, -10b, -21-5p, -30c, -155 and -212) overall, and for four miRs (-10a, -10b, -21-5p and -30c) at shorter follow-up time between blood collection and diagnosis (≤5 yr, ≤2 yr), were statistically significantly associated with risk. A score based on the panel showed a linear dose-response trend with risk (p-value = 0.0006). For shorter follow-up (≤5 yr), AUC for the score was 0.73, and for individual miRs ranged from 0.73 (miR-212) to 0.79 (miR-21-5p).

Fibroblast miR-210 overexpression is independently associated with clinical failure in Prostate Cancer - a multicenter (in situ hybridization) study

There is a need for better prognostication in prostate cancer (PC). “The micromanager of hypoxia”, microRNA-210 (miR-210) is directly linked to hypoxia, is overexpressed in PC and has been implied in tumor cell-fibroblast crosstalk. We investigated the prognostic impact of miR-210 in tumor cells and fibroblasts in PC. Tumor and stromal samples from a multicenter PC cohort of 535 prostatectomy patients were inserted into tissue microarrays. To investigate the expression of miR-210, we used in situ hybridization and two pathologists semiquantitatively scored its expression. Overexpression of miR-210 in tumor cells was not associated to biochemical failure-free survival (BFFS, p = 0.85) or clinical failure-free survival (CFFS, p = 0.09). However, overexpression of miR-210 in fibroblasts was significantly associated to a poor CFFS (p = 0.001), but not BFFS (p = 0.232). This feature was validated in both cohorts. Overexpression of miR-210 was independently associated with a reduced CFFS (HR = 2.76, CI 95% 1.25–6.09, p = 0.012). Overexpression of miR-210 in fibroblasts is independently associated with a poor CFFS. This highlights the importance of fibroblasts and cellular compartment crosstalk in PC. miR-210 is a candidate prognostic marker and potential therapeutic target in PC.

Organized metabolic crime in prostate cancer: The coexpression of MCT1 in tumor and MCT4 in stroma is an independent prognosticator for biochemical failure

BACKGROUND

Lactate import or export over cell membranes is facilitated by monocarboxylate transporters (MCTs) 1 and 4. Expression profiles can be markers of an oxidative or glycolytic phenotype. Descriptive studies and functional studies in neoplastic cells and fibroblasts in prostate cancer (PC) have suggested a distinct phenotype. We aimed to explore expression of MCT1 and MCT4 in PC cells and surrounding stroma in a large cohort. Additionally, we wanted to find out if distinct expression profiles were associated with biochemical failure-free survival (BFFS).

METHODS

Tissue microarrays were constructed from 535 patients with radical prostatectomies between January 1, 1995, and December 31, 2005. Immunohistochemistry was used to detect expression, and degrees of expression were evaluated semiquantitatively by 2 pathologists using light microscopy.

RESULTS

For MCT1, there was only epithelial expression, whereas there was a low level of expression of MCT4 in tumor and stroma. A total of 172 patients had a low expression of MCT1 in tumor and MCT4 in stroma. There were 232 patients who had a high expression of MCT1 and a low expression of MCT4 in stroma. Only 11 patients had a low tumoral MCT1 expression and a high stromal MCT4 expression, and 26 patients (5%) had a high expression of both. Patients with a high-high combination had a significantly reduced BFFS (P = 0.011), and when adjusting for other factors, its effect was significant and independent (HR = 1.99, CI 95%: 1.09-3.62; P = 0.024).

CONCLUSIONS

This study adds to the current understanding of the reversed Warburg effect to be a significant phenotype in PC. High coexpression of MCT1 in tumor and MCT4 in stroma is independently associated to a worse BFFS, and the strength of this association is as strong as having a Gleason score of ≥9.

Light desorption from an yttrium neutralizer for Rb and Fr magneto-optical trap loading

We present here the first evidence of photodesorption induced by low-intensity non-resonant light from an yttrium thin foil, which works as a neutralizer for Rb and Fr ions beam. Neutral atoms are suddenly ejected from the metal surface in a pulsed regime upon illumination with a broadband flash light and then released in the free volume of a pyrex cells. Here atoms are captured by a Magneto-Optical Trap (MOT), which is effectively loaded by the photodesorption. Loading times of the order of the flash rise time are measured. Desorption is also obtained in the continuous regime, by exploiting CW visible illumination of the metallic neutralizer surface. We demonstrate that at lower CW light intensities vacuum conditions are not perturbed by the photodesorption and hence the MOT dynamics remains unaffected, while the trap population increases thanks to the incoming desorbed atoms flux. Even with the Y foil at room temperature and hence with no trapped atoms, upon visible illumination, the number of trapped atoms reaches 10(5). The experimental data are then analyzed by means of an analytical rate equation model, which allows the analysis of this phenomenon and its dynamics and allows the determination of critical experimental parameters and the test of the procedure in the framework of radioactive Francium trapping. In this view, together with an extensive investigation of the phenomenon with (85)Rb, the first demonstration of the photodesorption-aided loading of a (210)Fr MOT is shown.

A room-temperature alternating current susceptometer--data analysis, calibration, and test

An AC susceptometer operating in the range of 10 Hz to 100 kHz and at room temperature is designed, built, calibrated, and used to characterize the magnetic behaviour of coated magnetic nanoparticles. Other weakly magnetic materials (in amounts of some millilitres) can be analyzed as well. The setup makes use of a digital acquisition system in order to determine the amplitude and the phase of the sample magnetization as a function of the frequency of the driving magnetic field, which is powered by a digital waveform generator. A specific acquisition strategy makes the response directly proportional to the sample susceptibility, taking advantage of the differential nature of the coil assembly. A calibration method based on conductive samples is developed.

Stray magnetic field compensation with a scalar atomic magnetometer

We describe a system for the compensation of time-dependent stray magnetic fields using a dual channel scalar magnetometer based on nonlinear Faraday rotation in synchronously optically pumped Cs vapor. We detail the active control strategy, with an emphasis on the electronic circuitry, based on a simple phase-locked-loop integrated circuit. The performance and limits of the system developed are tested and discussed. The system was applied to significantly improve the detection of free induction decay signals from protons of remotely magnetized water precessing in an ultralow magnetic field.

All-optical magnetometry for NMR detection in a micro-Tesla field and unshielded environment

An all-optical atomic magnetometer is used to detect a proton free-precession signal from a water sample polarized in a 0.7 T field and remotely analyzed in a 4 microT field. Nuclear spins are manipulated either by pi/2 pulses or by non-adiabatic rotation. The magnetometer operates at room temperature, in an unshielded environment and has a dual-channel sensor for differential measurements.

Full control of sodium vapor density in siloxane-coated cells using blue LED light-induced atomic desorption

We propose and experimentally implement a method, based on light-induced atomic desorption, for controlled generation of large sodium densities in siloxane-coated cells, kept at room temperature. An array of blue LEDs is used to desorb sodium atoms from the cell walls. The required atomic vapor density is achieved and stabilized by controlling the LED power through the feedback given by the sodium fluorescence. We show that sodium densities corresponding to about 400 K can be obtained and kept stable for a long time with less than 6 mW of LED light power. Moreover, this technique allows for precise vapor density modulation with a frequency of tenths of hertz, which is not possible using traditional heating methods.

Accurate measurements of transition frequencies and isotope shifts of laser-trapped francium

An interferometric method is used to improve the accuracy of the 7S-7P transition frequencies of three francium isotopes by 1 order of magnitude. The deduced isotope shifts for 209-211Fr confirm the ISOLDE data. The frequency of the D2 transition of 212Fr--the accepted reference for all Fr isotope shifts--is revised, and a significant difference with the ISOLDE value is found. Our results will be a benchmark for the accuracy of the theory of Fr energy levels, a necessary step to investigate fundamental symmetries.

Optical recording in Rb loaded-porous glass by reversible photoinduced phase transformations

We report reversible phase transformations in Rb loaded-porous glass irradiated with weak laser light which allow us to realize image storage on it. The effect is due to photo-induced changes of Rb distribution inside the glass pores, where atomic photodetachment and confinement produce either formation or evaporation of Rb nanoclusters. These processes depend on light frequency and intensity making controllable by light the porous glass transparency. We demonstrate that porous glass doped with Rb can be used as a support to record a light pulse for a long time as well as to remember the order of light colors in an illumination sequence.

Light induced atomic desorption from dry-film coatings

We report the first experimental evidence of nonthermal light induced atomic desorption (LIAD) from octadecyltrichlorosilane dry film. The experiment has been made with Rb confined in a coated cell kept at room temperature. A detailed study of the main features of LIAD effect has been made by varying intensity and wavelength of desorbing light. A discussion about the differences and similarities with other organic films that were studied first is reported. This result is important as it expands the list of materials showing such an effect and increases the possibilities to get suitable light controlled atomic sources for spectroscopy and applications. In particular, we plan to exploit this feature in a Fr magneto-optical trap apparatus.

Reversible light-controlled formation and evaporation of rubidium clusters in nanoporous silica

We observe reversible light assisted formation and evaporation of rubidium clusters embedded in nanoporous silica. Metallic nanoparticles are cyclically produced and evaporated by weak blue-green and near-infrared light, respectively. The atoms photodetached from the huge surface of the silica matrix build up clusters, whereas cluster evaporation is increased by induced surface plasmon excitation. Frequency tuning of light activates either one process or the other and the related changes of glass transparency become visible to the naked eye. We demonstrate that the porous silica, loaded with rubidium, shows memory of illumination sequences behaving as a rereadable and rewritable optical medium. These processes take place as a consequence of the strong confinement of atoms and particles at the nanoscale.

Coherent population trapping spectra in presence of ac magnetic fields

Experimental and theoretical investigations are reported on the effects induced by an alternating magnetic field on coherent population trapping resonances. We show that the ac magnetic field produces sidebands of these resonances in such a way that the spectrum observed is similar to those observed via the FM spectroscopic technique. Because of the very narrow linewidth of the resonances, sidebands are resolved even for ac field frequencies as low as a fraction of a kHz. The theoretical model developed, which takes into account a very simple atomic structure, fits the experimental data quite well.

Explosive vaporization of metallic sodium microparticles by CW resonant laser radiation

Explosive vaporization of metallic Na microparticles stimulated by resonant cw laser radiation has been observed in a glass cell. Vaporization occurs at low laser-power density. The effect consists in the generation of optically thick and sharply localized Na vapor clouds propagating in the cell against the laser beam. The effect is explained by laser excitation of Na atoms, which collide onto the surface of the microparticles and transfer their internal energy. This causes other atoms to be vaporized and to continue the avalanche process.

A beta-thalassaemia allele with 3 base substitution in codons 4/5 & 6 (ACT CCT GAG-> ACA TCT TAG) detected by denaturing gradient gel electrophoresis & sequencing

We report the analysis of a beta-thalassaemia gene involving three bases in codons 4/5 and 6 (ACT CCT GAG-> ACA TCT TAG) in a confirmed carrier whose child had beta-thalassaemia major. The fragment of the gene carrying the mutation was detected by denaturing gradient gel electrophoresis (DGGE) using GC clamped primers, followed by direct sequencing. DGGE analysis indicated that one gene was the wild type (normal) while the sequence changes observed were all in the other gene causing beta-thalassaemia major in the child. This confirms a single case report from Lucknow (UP) and adds to the beta-thalassaemia mutations identified in the beta-globin gene in India and will help in the thalassaemia control programme.

Diode laser spectroscopy of methane overtone transitions

With the aid of commercial room-temperature AlGaAs diode lasers, frequency modulation absorption spectroscopy was performed on the 7900 A and 8600 A rovibrational combination overtone bands of methane. Three weak transitions are reported in the range around 8610 A that, to our knowledge, have not yet been observed and measured. Self-broadening and pressure-broadening coefficients of one ofthese new absorption features (at 8608.93 A) were derived from CH(4) and for CH(4) immersed in N(2) and He buffer gases. An evaluation of the methane detection sensitivity is given for favorable laboratory conditions as well as for an open-path situation.