All-fiber multimode interferometer for the generation of a switchable multi-wavelength thulium-doped fiber laser

A compact all-fiber multimode interferometer (MMI) designed to produce a switchable multi-wavelength thulium-doped fiber laser (TDFL) is proposed and demonstrated. The TDFL fiber ring cavity employs a 60-cm-long multimode fiber into the cavity to induce multimode interference and provide intensity-dependent loss in order to generate a multi-wavelength output. The suppression of mode competition and the overall stability of the TDFL are further improved by exploiting the filtering capability of a Sagnac loop. By increasing the pump power, a switchable wavelength output is allowed with a wavelength spacing of ∼1.8  nm. At 361 mW input pump power, nine laser lines are generated, with a maximum signal-to-noise ratio value of ∼36  dB and an output power of 3.3 mW. The multi-wavelength TDFL also exhibits great stability in one-hour operation with a wavelength drift of 0.2 nm. The proposed multi-wavelength TDFL has potential to be employed in future thulium-doped fiber amplifier-based telecommunication infrastructure and also may be applicable in areas such as sensing and spectroscopy, largely associated with its 2 μm wavelength output.

The impact of anticancer activity upon Beta vulgaris extract mediated biosynthesized silver nanoparticles (ag-NPs) against human breast (MCF-7), lung (A549) and pharynx (Hep-2) cancer cell lines

The present study tried for a phyto-synthetic method of producing silver nanoparticles (Ag-NPs) with size controlled as and eco-friendly route that can lead to their advanced production with decorative tranquil morphology. By inducing temperature fluctuation of the reaction mixture from 25 to 80°C the plasmon resonance band raised slowly which had an ultimate effect on size and shape of Ag-NPs as shown by UV-visible spectroscopy and TEM results. The biosynthesized nanoparticles showed good cytotoxic impact against MCF-7, A549 and Hep2 cells compared to normal cell lines. Compared to control plates, the percentage of cell growth inhibition was found to be high with as concentrations of Ag-NPs becomes more as determined by MTT assay. The AO/EtBr staining observations demonstrated that the mechanism of cell death induced by Ag-NPs was due to apoptosis in cancer cells. These present results propose that the silver nanoparticles (Ag-NPs) may be utilized as anticancer agents for the treatment of various cancer types. However, there is a need for study of in vivo examination of these nanoparticles to find their role and mechanism inside human body. Further, studies we plan to do biomarker fabrication from the green synthesized plant extract nanoparticles like silver, gold and copper nanoparticles with optimized shape and sizes and their enhancement of these noble nanoparticles.

Tunable passively Q-switched thulium-fluoride fiber laser in the S+/S band (1450.0 to 1512.0 nm) region using a single-walled carbon-nanotube-based saturable absorber

A tunable passively Q-switched for S+/S band thulium-fluoride fiber (TFF) laser using single-walled carbon nanotubes as a saturable absorber is proposed and demonstrated. The tunability of the proposed laser covers a wavelength region of 1450.0-1512.0 nm, with a range of 62.0 nm. Stable Q-switched operation can be obtained at a pump power of 115.7-229.9 mW at 1492.0 nm. The resulting pulses have a measured repetition rate and pulse width of 12.0-36.4 kHz and 6.2-3.6 μs, respectively. The maximum pulse energy that was achieved in this experiment is 122.8 nJ. To the author's knowledge, this is the first reported tunable passively Q-switched TFF laser that covers the S+/S region that has been demonstrated.

Patients with chronic dizziness following traumatic head injury typically have multiple diagnoses involving combined peripheral and central vestibular dysfunction

OBJECTIVE

We hypothesised that chronic vestibular symptoms (CVS) of imbalance and dizziness post-traumatic head injury (THI) may relate to: (i) the occurrence of multiple simultaneous vestibular diagnoses including both peripheral and central vestibular dysfunction in individual patients increasing the chance of missed diagnoses and suboptimal treatment; (ii) an impaired response to vestibular rehabilitation since the central mechanisms that mediate rehabilitation related brain plasticity may themselves be disrupted.

METHODS

We report the results of a retrospective analysis of both the comprehensive clinical and vestibular laboratory testing of 20 consecutive THI patients with prominent and persisting vestibular symptoms still present at least 6months post THI.

RESULTS

Individual THI patients typically had multiple vestibular diagnoses and unique to this group of vestibular patients, often displayed both peripheral and central vestibular dysfunction. Despite expert neuro-otological management, at two years 20% of patients still had persisting vestibular symptoms.

CONCLUSION

In summary, chronic vestibular dysfunction in THI could relate to: (i) the presence of multiple vestibular diagnoses, increasing the risk of 'missed' vestibular diagnoses leading to persisting symptoms; (ii) the impact of brain trauma which may impair brain plasticity mediated repair mechanisms. Apart from alerting physicians to the potential for multiple vestibular diagnoses in THI, future work to identify the specific deficits in brain function mediating poor recovery from post-THI vestibular dysfunction could provide the rationale for developing new therapy for head injury patients whose vestibular symptoms are resistant to treatment.

Predictors of clinical recovery from vestibular neuritis: a prospective study

We sought to identify predictors of symptomatic recovery in vestibular neuritis. Forty VN patients were prospectively studied in the acute phase (median = 2 days) and 32 in the recovery phase (median = 10 weeks) with vestibulo‐ocular reflex, vestibular‐perceptual, and visual dependence tests and psychological questionnaires. Clinical outcome was Dizziness Handicap Inventory score at recovery phase. Acute visual dependency and autonomic arousal predicted outcome. Worse recovery was associated with a combination of increased visual dependence, autonomic arousal, anxiety/depression, and fear of bodily sensations, but not with vestibular variables. Findings highlight the importance of early identification of abnormal visual dependency and concurrent anxiety.

Functional neuroimaging of visuo-vestibular interaction

The brain combines visual, vestibular and proprioceptive information to distinguish between self- and world motion. Often these signals are complementary and indicate that the individual is moving or stationary with respect to the surroundings. However, conflicting visual motion and vestibular cues can lead to ambiguous or false sensations of motion. In this study, we used functional magnetic resonance imaging to explore human brain activation when visual and vestibular cues were either complementary or in conflict. We combined a horizontally moving optokinetic stimulus with caloric irrigation of the right ear to produce conditions where the vestibular activation and visual motion indicated the same (congruent) or opposite directions of self-motion (incongruent). Visuo-vestibular conflict was associated with increased activation in a network of brain regions including posterior insular and transverse temporal areas, cerebellar tonsil, cingulate and medial frontal gyri. In the congruent condition, there was increased activation in primary and secondary visual cortex. These findings suggest that when sensory information regarding self-motion is contradictory, there is preferential activation of multisensory vestibular areas to resolve this ambiguity. When cues are congruent, there is a bias towards visual cortical activation. The data support the view that a network of brain areas including the posterior insular cortex may play an important role in integrating and disambiguating visual and vestibular cues.

Differential effect of visual motion adaption upon visual cortical excitability

The objectives of this study were 1) to probe the effects of visual motion adaptation on early visual and V5/MT cortical excitability and 2) to investigate whether changes in cortical excitability following visual motion adaptation are related to the degree of visual dependency, i.e., an overreliance on visual cues compared with vestibular or proprioceptive cues. Participants were exposed to a roll motion visual stimulus before, during, and after visual motion adaptation. At these stages, 20 transcranial magnetic stimulation (TMS) pulses at phosphene threshold values were applied over early visual and V5/MT cortical areas from which the probability of eliciting a phosphene was calculated. Before and after adaptation, participants aligned the subjective visual vertical in front of the roll motion stimulus as a marker of visual dependency. During adaptation, early visual cortex excitability decreased whereas V5/MT excitability increased. After adaptation, both early visual and V5/MT excitability were increased. The roll motion-induced tilt of the subjective visual vertical (visual dependence) was not influenced by visual motion adaptation and did not correlate with phosphene threshold or visual cortex excitability. We conclude that early visual and V5/MT cortical excitability is differentially affected by visual motion adaptation. Furthermore, excitability in the early or late visual cortex is not associated with an increase in visual reliance during spatial orientation. Our findings complement earlier studies that have probed visual cortical excitability following motion adaptation and highlight the differential role of the early visual cortex and V5/MT in visual motion processing.NEW & NOTEWORTHY We examined the influence of visual motion adaptation on visual cortex excitability and found a differential effect in V1/V2 compared with V5/MT. Changes in visual excitability following motion adaptation were not related to the degree of an individual's visual dependency.

Introgression of chromosome segments from multiple alien species in wheat breeding lines with wheat streak mosaic virus resistance

Pyramiding of alien-derived Wheat streak mosaic virus (WSMV) resistance and resistance enhancing genes in wheat is a cost-effective and environmentally safe strategy for disease control. PCR-based markers and cytogenetic analysis with genomic in situ hybridisation were applied to identify alien chromatin in four genetically diverse populations of wheat (Triticum aestivum) lines incorporating chromosome segments from Thinopyrum intermedium and Secale cereale (rye). Out of 20 experimental lines, 10 carried Th. intermedium chromatin as T4DL*4Ai#2S translocations, while, unexpectedly, 7 lines were positive for alien chromatin (Th. intermedium or rye) on chromosome 1B. The newly described rye 1RS chromatin, transmitted from early in the pedigree, was associated with enhanced WSMV resistance. Under field conditions, the 1RS chromatin alone showed some resistance, while together with the Th. intermedium 4Ai#2S offered superior resistance to that demonstrated by the known resistant cultivar Mace. Most alien wheat lines carry whole chromosome arms, and it is notable that these lines showed intra-arm recombination within the 1BS arm. The translocation breakpoints between 1BS and alien chromatin fell in three categories: (i) at or near to the centromere, (ii) intercalary between markers UL-Thin5 and Xgwm1130 and (iii) towards the telomere between Xgwm0911 and Xbarc194. Labelled genomic Th. intermedium DNA hybridised to the rye 1RS chromatin under high stringency conditions, indicating the presence of shared tandem repeats among the cereals. The novel small alien fragments may explain the difficulty in developing well-adapted lines carrying Wsm1 despite improved tolerance to the virus. The results will facilitate directed chromosome engineering producing agronomically desirable WSMV-resistant germplasm.

Thermodynamics of the Adsorption of Cobalt on Lead Dioxide from Aqueous Solution

The adsorption of cobalt on lead dioxide from aqueous solutions has been optimized with respect to the shaking time, the amount of adsorbent, the pH and the concentration of adsorbate at 293 K. Under such optimum conditions, the adsorption of cobalt on lead dioxide has been studied at different temperatures and the process found to be endothermic with the distribution coefficient (KD) increasing with increasing temperature. The data fitted very well to the Langmuir, Freundlich and Dubinin–adushkevich isotherms, allowing the corresponding constants to be calculated. Values of ΔH0 and ΔS0 were calculated from the slope and intercept of the plots of In KD versus 1/T. The value of ΔG0, which decreased with increasing temperature, showed that the adsorption is more favourable at higher temperatures.

Estimation and Removal of Chromium Ions from Tannery Wastes Using Zeolite-3A

The concentration of potentially toxic chromium metal ions in sediments and liquid waste samples from selected tanneries was measured by atomic absorption spectrophotometry after digestion with nitric acid. The data obtained revealed the presence of elevated levels of chromium metal ions in waste samples relative to the NEQS (National Environmental Quality Standards) require-ments. A new process entitled IERECHROM (Ion Exchange REmoval of CHROMium) has been developed for the removal and separation of chromium ions from sediments using zeolite-3A. The factors affecting chromium ion removal include exchanger concentration, pH, shaking time and temperature. The applicability of the Freundlich. Dubinin–Radushkevich and virial isotherm equations to the system has been examined. The thermodynamic parameters °LH0, °LG0 and °LS0 were calculated using the virial isotherm expression. The results suggest that natural aluminosilicates such as zeolite-3A can be utilised as low-cost ion-exchange and sorbent materials because of their selectivities for the removal of chromium ions and various other heavy metals.

HVSI polymorphism indicates multiple origins of mtDNA in the Hazarewal population of Northern Pakistan

Mitochondrial DNA (mtDNA) is an important tool used to explore ethnogenetics and the evolutionary history of human populations. In this study, hypervariable segment I (HVSI) from mtDNA was analyzed to establish the genetic lineage of the Hazarewal populations residing in the Mansehra and Abbottabad districts of Northern Pakistan. HVSI was extracted from genetic specimens obtained from 225 unrelated male and female individuals belonging to seven distinct Pakistani ethnic groups (31 Abbassis, 44 Awans, 38 Gujars, 16 Jadoons, 23 Karlals, 33 Syeds, and 40 Tanolis). Eighty-three haplogroups, 39 of which were unique, were identified; haplogroup H was predominantly represented (in 40% of the people), followed by haplogroups M (21.78%), R (16.89%), N (15.56%), L (3.11%), and HV (2.67%). The results revealed a sex-biased genetic contribution from putative West Eurasian, South Asian, and Sub-Saharan populations to the genetic lineage of Hazarewal ancestry, with the effect of Eurasians being predominant. The HVSI nucleotide sequences exhibited some characteristic deletion mutations between 16,022 and 16,193 bp, which is characteristic of specific ethnic groups. HVSI sequence homology showed that Hazarewal populations fall into three major clusters: Syeds and Awans sorted out into cluster I; Tanolis, Gujars, and Karlals segregated in cluster II; and Abbassis and Jadoons in cluster III. Here, we have reported the firsthand genetic information and evolutionary sketch of the selected populations residing alongside the historical Silk Route, which provides a baseline for collating the origin, route of migration, and phylogenetics of the population.

An electrochemical platform for localized pH control on demand

Solution pH is a powerful tool for regulating many kinds of chemical activity, but is generally treated as a static property defined by a pre-selected buffer. Introducing dynamic control of pH in space, time, and magnitude can enable richer and more efficient chemistries, but is not feasible with traditional methods of titration or buffer exchange. Recent reports have featured electrochemical strategies for modifying bulk pH in constrained volumes, but only demonstrate switching between two preset values and omit spatial control entirely. Here, we use a combination of solution-borne quinones and galvanostatic excitation to enable quantitative control of pH environments that are highly localized to an electrode surface. We demonstrate highly reproducible acidification and alkalinization with up to 0.1 pH s(-1) (±0.002 pH s(-1)) rate of change across the dynamic range of our pH sensor (pH 4.5 to 7.5) in buffered solutions. Using dynamic current control, we generate and sustain 3 distinct pH microenvironments simultaneously to within ±0.04 pH for 13 minutes in a single solution, and we leverage these microenvironments to demonstrate spatially-resolved, pH-driven control of enzymatic activity. In addition to straightforward applications of spatio-temporal pH control (e.g. efficiently studying pH-dependencies of chemical interactions), the technique opens completely new avenues for implementing complex systems through dynamic control of enzyme activation, protein binding affinity, chemical reactivity, chemical release, molecular self-assembly, and many more pH-controlled processes.

Tunable Q-switched fiber laser using zinc oxide nanoparticles as a saturable absorber

Nanomaterials have ignited new interest due to their distinctive electronic, mechanical, and optical properties. Zinc oxide nanostructures are fabricated into thin film and then inserted between two fiber ferrules to act as a saturable absorber (SA). The modulation depth and insertion loss of the SA are 5% and 3.5 dB, respectively. When the ZnO-SA is incorporated into the laser cavity, a stable Q-switched pulse tunable from 1536 to 1586 nm (50 nm range) with pulse energy up to 46 nJ was observed. Our result suggests that ZnO is a promising broadband SA to generate passively Q-switched fiber lasers.

Photo-induced reduction of graphene oxide coating on optical waveguide and consequent optical intermodulation

Increased absorption of transverse-magnetic (TM) - polarised light by a graphene-oxide (GO) coated polymer waveguide has been observed in the presence of transverse-electric (TE) - polarised light. The GO-coated waveguide exhibits very strong photo-absorption of TE-polarised light - and acts as a TM-pass waveguide polariser. The absorbed TE-polarised light causes a significant temperature increase in the GO film and induces thermal reduction of the GO, resulting in an increase in optical-frequency conductivity and consequently increased optical propagation loss. This behaviour in a GO-coated waveguide gives the action of an inverted optical switch/modulator. By varying the incident TE-polarised light power, a maximum modulation efficiency of 72% was measured, with application of an incident optical power level of 57 mW. The GO-coated waveguide was able to respond clearly to modulated TE-polarised light with a pulse duration of as little as 100 μs. In addition, no wavelength dependence was observed in the response of either the modulation (TE-polarised light) or the signal (TM-polarised light).

Passively Q-switched erbium-doped fiber laser at C-band region based on WS₂ saturable absorber

We demonstrate a Q-switched erbium-doped fiber laser using tungsten disulfide (WS₂) as a saturable absorber. The WS₂ is deposited onto fiber ferrules using a drop-casting method. Passive Q-switched pulses operating in the C-band region with a central wavelength of 1560.7 nm are successfully generated by a tunable pulse repetition rate ranging from 27.2 to 84.8 kHz when pump power is increased from 40 to 220 mW. At the same time, the pulse width decreases from a maximum value of 3.84 μs to a minimum value of 1.44 μs. The signal-to-noise ratio gives a stable value of 43.7 dB. The modulation depth and saturation intensity are measured to be 0.99% and 36.2  MW/cm², respectively.

Tunable dual-wavelength ytterbium-doped fiber laser using a strain technique on microfiber Mach-Zehnder interferometer

In this paper, stable dual-wavelength generation using a strain technique for a ytterbium-doped fiber laser is successfully demonstrated. A microfiber-based Mach-Zehnder interferometer is inserted into the laser ring cavity and stretched using the xyz translation stage. Four sets of dual-wavelength output lasing are obtained when the strain is applied onto a microfiber. The dual-wavelength output possesses spacing between 7.12 and 11.59 nm, with displacement from 2 to 190 μm from the central wavelength. The obtained side-mode suppression ratio is ∼48  dBm, while the maximum power fluctuation and wavelength shift are less than 0.6 dB and 0.01 nm, respectively. The results demonstrate that this setup generates a stable dual-wavelength laser in the 1 μm region.

Black phosphorus crystal as a saturable absorber for both a Q-switched and mode-locked erbium-doped fiber laser

We report a simple way to generate Q-switched and mode-locked pulses by incorporating black phosphorus (BP) as a saturable absorber (SA) in an erbium-doped fiber laser (EDFL) cavity.

Applications of neuromodulation to explore vestibular cortical processing; new insights into the effects of direct current cortical modulation upon pursuit, VOR and VOR suppression

Functional imaging, lesion studies and behavioural observations suggest that vestibular processing is lateralised to the non-dominant hemisphere. Moreover, disruption of interhemispheric balance via inhibition of left parietal cortex using transcranial direct current stimulation (tDCS) has been associated with an asymmetric suppression of the vestibulo-ocular reflex (VOR). However, the mechanism by which the VOR was modulated remains unknown. In this paper we review the literature on non-invasive brain stimulation techniques which have been used to probe vestibular function over the last decade. In addition, we investigate the mechanisms whereby tDCS may modulate VOR, e.g. by acting upon pursuit, VOR suppression mechanisms or direct VOR modulation. We applied bi-hemispheric parietal tDCS in 11 healthy subjects and only observed significant effects on VOR gain (tdcs * condition p=0.041) - namely a trend for VOR gain increase with right anodal/left cathodal stimulation, and a decrease with right cathodal/left anodal stimulation. Hence, we suggest that the modulation of the VOR observed both here and in previous reports, is directly caused by top-down cortical control of the VOR as a result of disruption to interhemispheric balance, likely parietal.

ARE WHITE MATTER ABNORMALITIES A CAUSE OF ‘UNEXPLAINED DIZZINESS’? A RETROSPECTIVE BI–CENTRE STUDY

Introduction

Although cerebral small vessel disease is a significant contributor to the development of imbalance and falls in the elderly, whether it also contributes to the development of dizziness is not known.

Methods

A retrospective case analysis was conducted for 125 dizzy patients referred to two neuro-otology tertiary centres in London and Pisa. Specific search criteria of “white matter disease” was applied to databases and patients were divided into ‘explained’ causes of dizziness (ie benign positional vertigo, orthostatic hypotension, cerebellar ataxias) and ‘unexplained’ causes of dizziness. White matter hyperintensities (WMH) in MRI (T2 weighted and FLAIR) were blindly rated according to the Fazekas scale.

Results

61 patients (mean age=72SD=7.95 years) in the ‘unexplained’ group and 64 (mean age=72.01SD=8.28 years) in the ‘explained’ group were recruited. The overall frequency of lesions (Fazekas 1–3) differed between the groups (p=0.015). The frequency of severe lesions (Fazekas 3) was significantly higher in the unexplained group (21%) than in the explained group (5%; p=0.005).

Conclusion

Increased severity of WM abnormalities in cases of unexplained dizziness suggests that such abnormalities are contributory to the development of dizziness. WM lesions may induce dizziness either because patients perceive a degree of objective unsteadiness or by a cortical-subcortical disconnection syndrome.

USING TRANSCRANIAL MAGNETIC STIMULATION (TMS) TO PROBE EFFECTS OF VISUAL MOTION ADAPTATION ON PRIMARY VISUAL CORTEX (V1) EXCITABILITY IN BILATERAL VESTIBULAR FAILURE (BVF) PATIENTS

Background and aim

Patients with BVF report oscillopsia due to a defective vestibulo-ocular reflex causing retinal slip. No previous studies have probed visual cortical excitability using TMS and visual motion processing in these patients. We investigated the effects of visual motion adaptation on V1 cortical excitability in BVF patients and correlated this with psychophysical parameters.

Methods

12 BVF patients (7 males) aged 29–65 (mean=54.5) and 12 controls (6 males) aged 42–73 (mean=55) were recruited. Biphasic TMS pulses were applied at V1 and phosphene threshold (PT) was estimated. 3 measurement phases were (1) Stationary (2) Motion with optokinetic stimulation (OKS) Adaptation: OKS rightwards for 5 minutes 3) Post adaptation during viewing motion. All subjects completed questionnaires prior to the experiment. Results were analysed offline by calculating the probability of phosphene perception.

Results

Baseline phosphene thresholds were significantly higher in BVF patients (p=0.024) reflecting reduced visual cortical excitability. Lower oscillopsia scores correlated with reduced baseline V1 excitability (p=0.009).

Conclusions

This novel finding acts as a neurophysiological correlate for clinical observations of adaptive visual motion perception and is also correlated with psychophysical parameters. These results provide evidence for adaptive mechanisms leading to cortical plasticity following BVF.

ACQUIRED PENDULAR NYSTAGMUS IN STARGARDT'S SYNDROME SUPPRESSED BY ALCOHOL

Stargardts disease is the most common inherited form of juvenile macular degeneration leading to progressive visual loss. We describe a case of female twins aged 47 with Stargardt's Type III (rare autosomal dominant form) who, aged 7, developed blurred vision leading to identical progressive macular dystrophy and deterioration in visual acuities (both 1/60). Pendular nystagmus, presumably secondary to visual deprivation, was observed 4 years ago in both although only one twin (AW) described worsening horizontal oscillopsia, reportedly improving following alcohol consumption. Here, we report measurements of eye movements using 3D video-oculography at baseline and post alcohol ingestion (Blood alcohol concentrations: pre <10 mg/dl, post AW=66 mg/dl and HW=49 mg/dl). Analysis software was used to determine the amplitude and frequency of the pendular nystagmus. In AW peak-to-peak horizontal amplitude decreased from 5° (3.13 Hz) to 0.8°, and vertical amplitude from 2.9° (3.13 Hz) to 0.5°. In HW, peak horizontal amplitude reduced from 4.2° (3.22 Hz) to 1.5° and vertical amplitude from 1.9° (6.25 Hz) to 1.7°. In AW the oscillopsia resolved completely post-alcohol with modified oscillopsia scale scores reduced by 50%. (21/28 to 10/28). The findings demonstrate the potential effects of alcohol in suppressing pendular nystagmus and oscillopsia which may guide pharmacological treatments with alcohol-mimetics.

A Stable Dual-wavelength Thulium-doped Fiber Laser at 1.9 μm Using Photonic Crystal Fiber

A stable dual-wavelength thulium-doped fiber laser operating at 1.9 μm using a short length of photonic crystal fiber (PCF) has been proposed and demonstrated. The photonics crystal fiber was 10 cm in length and effectively acted as a Mach-Zehnder interferometry element with a free spectral range of 0.2 nm. This dual-wavelength thulium-doped fiber laser operated steadily at room temperature with a 45 dB optical signal-to-noise-ratio.

Are white matter abnormalities associated with "unexplained dizziness"?

Introduction

Although cerebral small vessel disease is a significant contributor to the development of imbalance and falls in the elderly, whether it causes dizziness is not known.

Methods

A retrospective case analysis was conducted for 122 dizzy patients referred to two neuro-otology tertiary centres in London and Pisa. Patients were divided into ‘explained’ causes of dizziness (e.g. benign positional vertigo, vestibular neuritis, orthostatic hypotension, cerebellar ataxias) and ‘unexplained’ dizziness. White matter hyperintensities (WMH) in MRI (T2 weighted and FLAIR sequences) were blindly rated according to the Fazekas scale.

Results

122 patients; 58 (mean age = 72, SD = 7.95 years) in the ‘unexplained’ group and 64 (mean age = 72.01, SD = 8.28 years) in the ‘explained’ group were recruited. The overall frequency of lesions (Fazekas 1–3) significantly differed between groups (p = 0.011). The frequency of severe lesions (Fazekas 3) was significantly higher in the ‘unexplained’ group (22%) than in the ‘explained’ group (5%; p = 0.003).

Conclusion

Increased severity of WMH in cases of unexplained dizziness suggests that such abnormalities are likely contributory to the development of dizziness. WM lesions may induce dizziness either because patients perceive a degree of objective unsteadiness or by a disconnection syndrome involving vestibular or locomotor areas of the brain.

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Retrospective analysis of 122 dizzy patients divided into explained and unexplained causes

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Severity of MRI white matter disease predicts unexplained dizziness, not vascular risk factors

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White matter lesions more severe in unexplained than in explained dizziness group

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White matter lesions likely contributory to development of unexplained dizziness

Anticancer Effects of Extracts from the Fruit of Morinda Citrifolia (Noni) in Breast Cancer Cell Lines

Morinda citrifolia L. (NONI) fruits have been used for thousands of years for the treatment of many health problems including cancer, cold, diabetes, flu, hypertension, and pain. Plant extracts have reported several therapeutic benefits, but extraction of individual compound from the extract often exhibits limited clinical utility as the synergistic effect of various natural ingredients gets lost. They generally constitute polyphenols and flavonoids. Studies have suggested that these phytochemicals, especially polyphenols, display high antioxidant properties, which help to reduce the risk of degenerative diseases, such as cancer and cardiovascular diseases. Several in-vitro and in-vivo studies have shown that Noni fruits have antioxidant, anti-inflammatory, anti-dementia, liver-protective, anticancer, analgesic, and immunomodulatory effects. Till date about 7 in vitro cancer studies have been done, but a detailed in vitro study including cell cycle and caspase activation assay on breast cancer cell line has not been done. In the present study different Noni fruit fractions have tested on cancer cell lines MCF-7, MDA-MB-231 (breast adenocarcinoma) and one non-cancer cell line HEK-293 (Human embryonic kidney). Out of which ethylacetate extract showed a higher order of in vitro anticancer activity profile. The ethylacetate extract strongly inhibited the proliferation of MCF-7, MDA-MB-231 and HEK-293 cell lines with IC50 values of 25, 35, 60 µg/ml respectively. The extract showed increase in apoptotic cells in MCF-7 and MDA-MB-231 cells and arrested the cell cycle in the G1/S phase in MCF-7 and G0/G1 phase in MDA-MB-231 cells. Noni extract also decreases the intracellular ROS generation and mitochondrial membrane potential.

Locomotor adaptation is modulated by observing the actions of others

Observing the motor actions of another person could facilitate compensatory motor behavior in the passive observer. Here we explored whether action observation alone can induce automatic locomotor adaptation in humans. To explore this possibility, we used the "broken escalator" paradigm. Conventionally this involves stepping upon a stationary sled after having previously experienced it actually moving (Moving trials). This history of motion produces a locomotor aftereffect when subsequently stepping onto a stationary sled. We found that viewing an actor perform the Moving trials was sufficient to generate a locomotor aftereffect in the observer, the size of which was significantly correlated with the size of the movement (postural sway) observed. Crucially, the effect is specific to watching the task being performed, as no motor adaptation occurs after simply viewing the sled move in isolation. These findings demonstrate that locomotor adaptation in humans can be driven purely by action observation, with the brain adapting motor plans in response to the size of the observed individual's motion. This mechanism may be mediated by a mirror neuron system that automatically adapts behavior to minimize movement errors and improve motor skills through social cues, although further neurophysiological studies are required to support this theory. These data suggest that merely observing the gait of another person in a challenging environment is sufficient to generate appropriate postural countermeasures, implying the existence of an automatic mechanism for adapting locomotor behavior.

Room temperature ammonia sensing using tapered multimode fiber coated with polyaniline nanofibers

We demonstrate an ammonia sensor composed of a tapered multimode fiber coated with polyaniline nanofibers that operates at room temperature (26°C). The optical properties of the polyaniline layer changes when it is exposed to ammonia, leading to a change in the absorption of evanescent field. The fiber sensor was tested by exposing it to ammonia at different concentrations and the absorbance is measured using a spectrophotometer system. Measured response and recovery times are about 2.27 minutes and 9.73 minutes, respectively. The sensor sensitivity can be controlled by adjusting the tapered fiber diameter and the highest sensitivity is achieved when the diameter is reduced to 20 µm.

Microbial biotransformation: a tool for drug designing (Review)

For centuries microbial biotransformation has proved to be an imperative tool in alleviating the production of various chemicals used in food, pharmaceutical, agrochemical and other industries. In the field of phar- maceutical research and development, biotransformation studies have been extensively applied to investigate the metabolism of compounds (leads, lead candidates, etc.) using animal models. The microbial biotransfor- mation phenomenon is then commonly employed in comparing metabolic pathways of drugs and scaling up the metabolites of interest discovered in these animal models for further pharmacological and toxicological evaluation. Microorganisms can conveniently afford drugs difficult obtained via synthesis. The plethora of reported microbial biotransformations along with its added benefits has already invoked further research in bioconversion of novel and structurally complex drugs. This review alternatively discusses the prospect of microbial biotransformation studies as a significant element ameliorating drug discovery and design in terms of cost-effectiveness, environment protection and greater structural diversity as compared to animal models used to study metabolism. To explicate the microbial biotransformation paradigm in drug designing 3 main areas in this aspect have been analyzed: 1--lead expansion: obtaining pharmacologically improved metabo- lites from bioactive molecules; 2--biosynthesis of precursors/intermediates involved in the production of bioactive molecules; 3--resolution of racemic mixture to obtain enantiomers possessing different pharma- cological profiles.

Generation and transmission of 3 × 3 W-Band multi-input multi-output orthogonal frequency division multiplexing-radio-over-fiber signals using micro-ring resonators

Using the micro-ring resonator (MRR) system, the single and multi-carriers at frequencies of f(1)=192.898, f(2)=192.990, f(3)=193.1, f(4)=193.315, and f(5)=193.537  THz with a free spectral range (FSR) of 92, 110, 215, and 222 GHz, respectively, are generated to be suitable for a radio-over-fiber (RoF) system based on multi-input multi-output (MIMO) with orthogonal frequency division multiplexing (OFDM). Demonstrated are the concepts of all-optical MIMO signal generation and its transmission over a 50 km single mode fiber (SMF) optical link and an up to 3 m wireless link. Sixty-four multi-carriers are used in the all-optical generation of three MIMO W-Band RF signals, where the single carriers (f(3)-f(5)) transport the signals over the RoF link. The bit error rate (BER) of the overall system performance is discussed; thus, the transmission of MIMO signals is feasible for up to an SMF path 50 km long and a wireless distance of 3 m.

Multiwall carbon nanotube polyvinyl alcohol-based saturable absorber in passively Q-switched fiber laser

In this work, we demonstrated a compact Q-switched erbium-doped fiber laser capable of generating high-energy pulses using a newly developed multiwall carbon nanotube (CNT) polyvinyl alcohol (PVA) thin film based saturable absorber. Q-switched pulse operation is obtained by sandwiching the thin film between two fiber ferrules forming a saturable absorber. A saturable absorber with 1.25 wt. % of PVA concentration shows a consistency in generating pulsed laser with a good range of tunable repetition rate, shortest pulse width, and produces a high pulse energy and peak power. The pulse train generated has a maximum repetition rate of 29.9 kHz with a corresponding pulse width of 3.49 μs as a function of maximum pump power of 32.15 mW. The maximum average output power of the Q-switched fiber laser system is 1.49 mW, which translates to a pulse energy of 49.8 nJ. The proposed method of multiwall CNT/PVA thin film fabrication is low in cost and involves uncomplicated processes.

Tunable single Stokes extraction from 20 GHz Brillouin fiber laser using ultranarrow bandwidth optical filter

The individual extraction of a Brillouin Stokes line from a 20 GHz comb generated from the compact configuration of a multiwavelength Brillouin fiber ring laser configuration has been achieved using an ultranarrow bandwidth (UNB) optical filter. The narrowest bandwidth transmission of a UNB optical filter that is 50 pm is used in order to get particular Stokes. The Stokes filtered is in the wavelength range of 1549.768-1551.016 nm. High SNR within the range of 54.97-11.73 dB with almost nil peak power loss being obtained was monitored by a 0.16 pm optical spectrum analyzer, giving convincing results. Relatively, the proposed configuration could provide wide tunability and narrow selection of the Brillouin Stokes.

Closely spaced dual-wavelength fiber laser using an ultranarrow bandwidth optical filter for low radio frequency generation

A dual-wavelength (DW) fiber laser with a closely spaced single longitudinal mode (SLM) output is proposed and demonstrated. The proposed fiber laser utilizes a conventional fiber Bragg grating with a center wavelength of about 1546.8 nm in conjunction with an ultranarrow bandwidth tunable optical filter to generate the desired DW SLM output. Observations with a very high resolution optical spectrum analyzer, which was capable of achieving resolutions up to 0.16 pm, revealed detailed spectral characteristics not characteristically seen before. A channel spacing of up to 58 nm was realized, and spacing as small as 2 pm was achieved. The minimum channel spacing and its resulting beat frequency are the narrowest observed yet to the best of our knowledge for a DW fiber laser at room temperature.

An insight into structure and stability of DNA in ionic liquids from molecular dynamics simulation and experimental studies

Molecular dynamics simulation and biophysical analysis were employed to reveal the characteristics and the influence of ionic liquids (ILs) on the structural properties of DNA. Both computational and experimental evidence indicate that DNA retains its native B-conformation in ILs. Simulation data show that the hydration shells around the DNA phosphate group were the main criteria for DNA stabilization in this ionic media. Stronger hydration shells reduce the binding ability of ILs' cations to the DNA phosphate group, thus destabilizing the DNA. The simulation results also indicated that the DNA structure maintains its duplex conformation when solvated by ILs at different temperatures up to 373.15 K. The result further suggests that the thermal stability of DNA at high temperatures is related to the solvent thermodynamics, especially entropy and enthalpy of water. All the molecular simulation results were consistent with the experimental findings. The understanding of the properties of IL-DNA could be used as a basis for future development of specific ILs for nucleic acid technology.

Photonic crystal fiber based dual-wavelength Q-switched fiber laser using graphene oxide as a saturable absorber

A Q-switched dual-wavelength fiber laser with narrow channel spacing is proposed and demonstrated. The fiber laser is built around a 3 m long erbium doped fiber as the gain medium and a 10 cm long photonic crystal fiber (PCF) as the element used to generate the dual-wavelength output. The PCF has a solid core approximately 4.37 μm in diameter and is surrounded by microscopic air-holes with a diameter of about 5.06 μm each as well as a zero-dispersion wavelength of about 980 nm. A graphene oxide based saturable absorber is used to generate the desired pulsed output. At the maximum pump power of 72 mW the laser is capable of generating pulses with a repetition rate and pulse-width of 31.0 kHz and 7.0 μs, respectively, as well as an average output power and pulse energy of 0.086 mW and 2.8 nJ, respectively. The proposed fiber laser has substantial potential for use in applications that require longer duration pulsed outputs such as in range finding and terahertz radiation generation.