Tranexamic acid, as an adjunct to oxytocin prophylaxis, in the prevention of postpartum haemorrhage in women undergoing elective caesarean section: A single-centre double-blind randomised controlled trial

OBJECTIVE

To evaluate the effectiveness of tranexamic acid (TXA) in reducing blood loss during elective caesarean sections in women with and without risk factors for postpartum haemorrhage (PPH).

DESIGN

A double-blind, randomised placebo-controlled trial.

SETTING

An academic tertiary referral centre in Singapore.

POPULATION

Multiethnic women aged 21 years or older undergoing elective caesarean section.

METHODS

Randomisation to intravenous TXA or normal saline (placebo) 10 minutes before skin incision.

MAIN OUTCOME MEASURES

Calculated estimated blood loss (cEBL), derived from blood volume and haematocrit levels.

RESULTS

Between June 2020 and October 2021, 200 women were randomised to the placebo or TXA groups. Women who received prophylactic TXA had a significantly lower mean cEBL compared with those receiving placebo (adjusted mean difference -126.4 mL, 95% CI -243.7 to -9.1, p = 0.035). The effect was greatest in those at high risk for PPH, with a reduction in cEBL (mean difference -279.6 mL, 95% CI -454.8 to -104.3, p = 0.002) and a lower risk of cEBL ≥500 mL (risk ratio [RR] 0.54, 95% CI 0.36-0.83, p = 0.007) and cEBL ≥1000 mL (RR 0.44, 95% CI 0.20-0.98, p = 0.016). Subgroup analysis showed benefit for women with preoperative haemoglobin <10.5 g/dL (mean difference -281.9 mL, 95% CI -515.0 to -48.8, p = 0.019). There was no significant difference in need for additional medical or surgical interventions. There were no maternal or neonatal adverse outcomes.

CONCLUSION

Prophylactic TXA should be considered in women with risk factors for PPH, and those most likely to benefit are those with preoperative haemoglobin <10.5 g/dL.

Ultrafast dynamics of hemin aggregates

The effects of solvents on the conformation of hemin and their implications on the dynamics of the complex have been studied using the time-resolved optical Kerr effect (OKE) with 35 fs laser pulses (at a central wavelength of 800 nm). The OKE enabled estimation to be made of the third-order nonlinear electronic susceptibility (χ⁽³⁾) of hemin solutions: it was found to be significantly smaller than that in hemin thin films. The real and imaginary components of χ⁽³⁾ were negative in both the solvents, suggesting that one-photon as well as two-photon absorption processes contribute to the nonlinear electronic susceptibility of hemin. Our study of the ultrafast heme dynamics not only unveils the instantaneous electronic response related to electronic susceptibility but also brings to the fore a novel libration process that has hitherto remained undetected. The hindered rotation in the femtosecond domain that may be responsible for this libration process possibly stems from π-π hemin oligomers formed in aqueous solution. The present results provide new insights into the conformational dynamics in the self-assembly of heme oligomers that may also be significant in certain pathogenic conditions where free heme is formed in biological systems.

Leishmania incidence and prevalence in U.S. hunting hounds maintained via vertical transmission

Leishmania is the causative agent of leishmaniasis, a deadly protozoan disease which affects over 1 million people each year. Autochthonous cases of canine leishmaniasis are generally associated with tropical and subtropical climatic zones. However, in 1999, U.S. hunting dogs were found to have leishmaniasis with no history of travel outside the country. Transmission of this disease was found to be primarily vertical. In endemic areas, dogs are a dominant domestic reservoir host for Leishmania infantum. This study evaluated L. infantum infection prevalence and incidence within US dogs tested over a nine-year span (2007-2015). This investigation used both passive and active surveillance, following an initial outbreak investigation by the Centers for Disease Control. L. infantum infection incidence and prevalence over time and across regions were examined to evaluate whether transmission was sufficient to maintain ongoing infection within this population. These studies also established whether this disease is becoming more or less prominent within this reservoir host, dogs. There was no significant difference between prevalence and incidence rates via as measured by passive vs. active surveillance. Although due to fluctuations in sample submission there were significant changes in both incidence and prevalence of L. infantum in US hunting dogs over this nine year span, these differences were not outside of the interquartile range and therefore there is likely to be a steady-state of transmission within U.S. dogs. Based on these findings, if vertical transmission is the primary means of L. infantum spread in U.S. dogs, with appropriate husbandry and infection control procedures, elimination of L. infantum from US dogs could be possible.

Inscription of type I and depressed cladding waveguides in lithium niobate using a femtosecond laser

We describe two types of waveguides (type I and depressed cladding) inscribed in lithium niobate using a variable repetition rate (200 kHz-25 MHz), 270 fs duration fiber laser. The type I modification-based waveguides have propagation losses in the range from 1.2 to 10 dB/cm at 1550 nm, depending on experimental parameters. These waveguides are not permanent; they deteriorate over time. Such deterioration of waveguides can be slowed down from 30 days to 100 days by pre-annealing the samples and by writing at a 720 kHz laser repetition rate. The propagation losses measured at 1550 nm show significant improvement for pre-annealed samples. The depressed cladding-inscribed waveguides are permanent, but the propagation loss depends on the number of damage tracks. A track separation of ∼1  μm between adjacent damage tracks yields the lowest propagation loss of 0.5 dB/cm at 1550 nm for a 40 μm diameter waveguide. We observe multimode guidance for sizes in the range of 20-80 μm in these waveguide structures at 1550 nm. Their crystalline nature is found to remain intact, as inferred from second-harmonic generation within the waveguide region.

Femtosecond supercontinuum generation in water in the vicinity of absorption bands

We show that it is possible to overcome the perceived limitations caused by absorption bands in water so as to generate supercontinuum (SC) spectra in the anomalous dispersion regime that extend well beyond 2000 nm wavelength. By choosing a pump wavelength within a few hundred nanometers above the zero-dispersion wavelength of 1048 nm, initial spectral broadening extends into the normal dispersion regime and, in turn, the SC process in the visible strongly benefits from phase-matching and matching group velocities between dispersive radiation and light in the anomalous dispersion regime. Some of the SC spectra are shown to encompass two and a half octaves.

Optical control of filamentation-induced damage to DNA by intense, ultrashort, near-infrared laser pulses

We report on damage to DNA in an aqueous medium induced by ultrashort pulses of intense laser light of 800 nm wavelength. Focusing of such pulses, using lenses of various focal lengths, induces plasma formation within the aqueous medium. Such plasma can have a spatial extent that is far in excess of the Rayleigh range. In the case of water, the resulting ionization and dissociation gives rise to in situ generation of low-energy electrons and OH-radicals. Interactions of these with plasmid DNA produce nicks in the DNA backbone: single strand breaks (SSBs) are induced as are, at higher laser intensities, double strand breaks (DSBs). Under physiological conditions, the latter are not readily amenable to repair. Systematic quantification of SSBs and DSBs at different values of incident laser energy and under different external focusing conditions reveals that damage occurs in two distinct regimes. Numerical aperture is the experimental handle that delineates the two regimes, permitting simple optical control over the extent of DNA damage.

Optically trapping tumor cells to assess differentiation and prognosis of cancers

We report an optical trapping method that may enable assessment of the differentiation status of cancerous cells by determining the minimum time required for cell-cell adhesion to occur. A single, live cell is trapped and brought into close proximity of another; the minimum contact time required for cell-cell adhesion to occur is measured using transformed cells from neural tumor cell lines: the human neuroblastoma SK-N-SH and rat C6 glioma cells. Earlier work on live adult rat hippocampal neural progenitors/stem cells had shown that a contact minimum of ~5 s was required for cells to adhere to each other. We now find the average minimum time for adhesion of cells from both tumor cell lines to substantially increase to ~20-25 s, in some cases up to 45 s. Upon in vitro differentiation of these cells with all-trans retinoic acid the average minimum time reverts to ~5-7 s. This proof-of-concept study indicates that optical trapping may be a quick, sensitive, and specific method for determining differentiation status and, thereby, the prognosis of cancer cells.

Selective breaking of bonds in water with intense, 2-cycle, infrared laser pulses

One of the holy grails of contemporary science has been to establish the possibility of preferentially breaking one of several bonds in a molecule. For instance, the two O-H bonds in water are equivalent: given sufficient energy, either one of them is equally likely to break. We report bond-selective molecular fragmentation upon application of intense, 2-cycle pulses of 800 nm laser light: we demonstrate up to three-fold enhancement for preferential bond breaking in isotopically substituted water (HOD). Our experimental observations are rationalized by means of ab initio computations of the potential energy surfaces of HOD, HOD(+), and HOD(2+) and explorations of the dissociation limits resulting from either O-H or O-D bond rupture. The observations we report present a formidable theoretical challenge that need to be taken up in order to gain insights into molecular dynamics, strong field physics, chemical physics, non-adiabatic processes, mass spectrometry, and time-dependent quantum chemistry.

Influencing supercontinuum generation by phase distorting an ultrashort laser pulse

We show that the spectral distribution of the supercontinuum (SC) generated in barium fluoride is amenable to alteration simply by controlling the second- and third-order phase distortion of incident femtosecond-duration pulses. The second- and third-order phase distortions are controlled by an acoustic-optic programmable dispersive filter (AOPDF). The spectral extent on the blue side of the SC is influenced by independently varying the phase distortion of an ultrashort laser pulse.

DNA damage by OH radicals produced using intense, ultrashort, long wavelength laser pulses

We probe femtosecond laser induced damage to aqueous DNA, relying on strong-field interaction with water wherein electrons and free radicals are generated in situ; these, in turn, interact with DNA plasmids under physiological conditions, producing nicks. Exposure to intense femtosecond pulses of 1350 and 2200 nm light induces single strand breaks and double strand breaks (DSBs) in DNA. At the longer wavelength (and at higher intensities), rotationally hot OH radicals induce DSBs, producing linear DNA. Strand breaks occur due to single or multiple OH hits on DNA. With 2200 nm light, DSBs are formed mostly by the action of two OH radicals; use of OH scavengers establishes that the probability of a two-hit event reduces much faster than a one-hit event as scavenger concentration is increased. Thermal effects do not induce DSBs with 2200 nm light.

Pituitary apoplexy with reversible cerebral vasoconstrictive syndrome after spinal anaesthesia for emergency caesarean section: an uncommon cause for postpartum headache

Pituitary apoplexy is a rare condition involving pituitary necrosis following either pituitary haemorrhage or infarction. Similarly, reversible cerebral vasoconstrictive syndrome is a cerebrovascular disorder characterised by diffuse, multifocal narrowing of cerebral arteries. Both may present with an acute, intense headache and associated neurological deficits. In postpartum women, these conditions should be considered in the differential diagnosis of post-dural puncture headache following regional anaesthesia, as serious morbidity may ensue if they are left untreated. We report the case of a patient who developed pituitary apoplexy during an emergency caesarean section under spinal anaesthesia. It was further complicated by the development of reversible cerebral vasoconstriction syndrome and stroke.

Carrier-envelope-phase effects in ultrafast strong-field ionization dynamics of multielectron systems: Xe and CS2

Carrier-envelope-phase- (CEP) stabilized 5 and 22 fs pulses of intense 800 nm light are used to probe the strong-field ionization dynamics of xenon and carbon disulfide. We compare ion yields obtained with and without CEP stabilization. With 8-cycle (22 fs) pulses, Xe(6+) yields are suppressed (relative to Xe(+)) by 30%-50%, depending on phase, reflecting the phase dependence of nonsequential ionization and its contribution to the formation of higher charge states. Ion yields for Xe(q+) (q = 2-4) with CEP-stabilized pulses are enhanced (by up to 50%) compared to those with CEP-unstabilized pulses. Such enhancement is particularly pronounced with 2-cycle (5 fs) pulses and is distinctly phase dependent. Orbital shape and symmetry affect how CS(2) responds to variations in optical field that are effected as CEP is altered, keeping intensity constant. Molecular fragmentation is found to depend on field strength (not intensity); the relative enhancement of fragmentation when CEP-stabilized 2-cycle pulses are used is found to be at the expense of molecular ionization.

Intense two-cycle laser pulses induce time-dependent bond hardening in a polyatomic molecule

A time-dependent bond-hardening process is discovered in a polyatomic molecule (tetramethyl silane, TMS) using few-cycle pulses of intense 800 nm light. In conventional mass spectrometry, symmetrical molecules such as TMS do not exhibit a prominent molecular ion (TMS(+)) as unimolecular dissociation into [Si(CH(3))(3)](+) proceeds very fast. Under a strong field and few-cycle conditions, this dissociation channel is defeated by time-dependent bond hardening: a field-induced potential well is created in the TMS(+) potential energy curve that effectively traps a wave packet. The time dependence of this bond-hardening process is verified using longer-duration (≥100 fs) pulses; the relatively slower falloff of optical field in such pulses allows the initially trapped wave packet to leak out, thereby rendering TMS(+) unstable once again.

Optical trapping in an absorbing medium: from optical tweezing to thermal tweezing

We report on optical trapping in a weakly absorbing medium, hemin, an iron-containing porphyrin that is an important component of hemoglobin. By altering the hemin concentration we are able to control the amount of optical energy that is absorbed; changing the hemin concentration from <12 mg/ml to >45 mg/ml enables the onset of thermal trapping to be observed. By estimating the trap strength using two different methods we are readily able to differentiate between the optical trapping and thermal trapping regimes. We also deduce the rise in temperature that occurs within the laser focal volume: temperature changes of 5-24 K are observed for laser power values of 10-90 mW for hemin concentrations of 0-50 mg/ml.

Effect of intense, ultrashort laser pulses on DNA plasmids in their native state: strand breakages induced by in situ electrons and radicals

Single strand breaks are induced in DNA plasmids, pBR322 and pUC19, in aqueous media exposed to strong fields generated using ultrashort laser pulses (820 nm wavelength, 45 fs pulse duration, 1 kHz repetition rate) at intensities of 1-12  TW cm(-2). The strong fields generate, in situ, electrons and radicals that induce transformation of supercoiled DNA into relaxed DNA, the extent of which is quantified. Introduction of electron and radical scavengers inhibits DNA damage; results indicate that OH radicals are the primary (but not sole) cause of DNA damage.

Prevalence and correlates of diabetes in South asian indians in the United States: findings from the metabolic syndrome and atherosclerosis in South asians living in america study and the multi-ethnic study of atherosclerosis

BACKGROUND

Individuals from South Asia have high diabetes prevalence despite low body weight. We compared the prevalence of diabetes among South Asian Indians with other U.S. ethnic groups and explored correlates of diabetes.

METHODS

This was a cross-sectional study of 150 South Asian Indians (ages 45-79) in California, using similar methods to the Multi-Ethnic Study of Atherosclerosis (MESA). Type 2 diabetes was classified by fasting plasma glucose (FPG) >or=126 mg/dL, 2-h postchallenge glucose >or=200 mg/dL, or use of hypoglycemic medication.

RESULTS

A total of 29% of Asian Indians had diabetes, 37% had prediabetes, and 34% had normal glucose tolerance. After full adjustment for covariates, Indians still had significantly higher odds of diabetes compared to whites and Latinos, but not significantly different from African Americans and Chinese Americans in MESA: Indians [odds ratio (OR), 1.0], whites [OR, 0.29; 95% confidence interval (CI), 0.17-0.49], Latinos (OR, 0.59; CI, 0.34-1.00) African Americans (OR, 0.77; CI 0.45-1.32), Chinese Americans (OR, 0.78, CI, 0.45-1.32). Variables associated with prediabetes or diabetes among Indians included hypertension, fatty liver, visceral adiposity, microalbuminuria, carotid intima media thickness, and stronger traditional Indian beliefs.

CONCLUSIONS

Indian immigrants may be more likely to have diabetes than other U.S. ethnic groups, and cultural factors may play a role, suggesting that this is a promising area of research.

Optical-tweezer-induced microbubbles as scavengers of carbon nanotubes

A modified optical tweezers set-up has been used to generate microbubbles in flowing, biologically relevant fluids and human whole blood that contains carbon nanotubes (CNTs) using low power (< or =5 mW), infrared (1064 nm wavelength), continuous wave laser light. Temperature driven effects at the tweezers' focal point help to optically trap these microbubbles. It is observed that proximate CNTs are driven towards the focal spot where, on encountering the microbubble, they adhere to it. Such CNT-loaded microbubbles can be transported both along and against the flow of surrounding fluid, and can also be exploded to cause fragmentation of the bundles. Thus, microbubbles may be used for scavenging, transporting and dispersal of potentially toxic CNTs in biologically relevant environments.

Bright visible emission from carbon nanotubes spatially constrained on a micro-bubble

We report emission of broadband light in the spectral range 500 nm - 900 nm from single walled carbon nanotubes (SWNTs) in a liquid environment upon irradiance by a very low power (typically <5 mW), continuous-wave laser source in a tweezers setup. We show (i) formation of micro-bubbles upon irradiation of fluids containing bundles of SWNTs, (ii) optical trapping of such micro-bubbles, (iii) adhesion of SWNTs on the surface of such micro-bubbles, and (iv) bright emission of white light due to tweezer-induced localized heating of spatially-constrained SWNTs.

Polarization and energy stability of filamentation-generated few-cycle pulses

Polarization properties and energy stability are measured for few-cycle pulses that are generated by filamentation in dual Ar-filled tubes in tandem. The dual-tube geometry enhances the contribution of self-phase modulation to spectral broadening. The polarization extinction ratio (I(perpendicular)/I(parallel) is improved for the beam transmitted through the second tube compared to the first tube and of the incident laser beam. Polarization control of few-cycle pulses is realized in simple fashion by a half-wave plate placed prior to the dual-tube assembly. We show that intensity clamping in the filament affords a major advantage in accomplishing a significant reduction in energy fluctuations compared to those inherent in the incident laser beam.

Ionization of Linear Alcohols by Strong Optical Fields

We have experimentally probed the strong-field ionization dynamics of gas-phase linear alcohols, methanol, ethanol, and 1-propanol, by irradiating them with intense, femtosecond-duration laser pulses of 800 and 400 nm wavelength. Specifically, we make high resolution measurements of the energies of electrons that are ionized by the action of the optical field. Our electron spectroscopy measurements enable us to bifurcate the dynamics into multiphoton ionization and tunneling ionization regimes. In the case of 800 nm irradiation, such bifurcation into different ionization regimes is reasonably rationalized within the framework of the adiabaticity parameter based on the original Keldysh-Faisal-Reiss model of atomic ionization, without recourse to any structure-dependent modifications to the theory. In that sense, our 800 nm spectroscopy indicates that the linear alcohols exhibit atom-like properties as far as strong field ionization dynamics in the multiphoton ionization and tunneling regimes are concerned. We also explore the limitations of this atom-like picture by making measurements with 400 nm photons wherein the ponderomotive potential experienced by the ionized electrons is much less than the photon energy; effects that are purely molecular then appear to influence the strong field dynamics.

Probing molecular symmetry effects in the ionization of N2 and O2 by intense laser fields

High-resolution electron spectroscopy is used to explore the role played by molecular symmetry in determining the morphology of the energy spectra of electrons ejected when N2 and O2 are irradiated by intense laser fields. In O2, the low-energy part of the electron spectrum is curtailed due to the destructive interference brought about by the antibonding nature of the O2 valence orbital. The high-energy tail of the spectrum is also suppressed by virtue of electron rescattering being of little consequence in O2. In contrast, in N2, which has a bonding valence orbital, the electron dynamics follow the pattern that has been established for atomic ionization in strong optical fields.

Femtosecond laser written channel waveguides in tellurite glass

We have made and characterized a new, erbium-doped tellurite glass that has high glass transition temperature. Addition of phosphate is found to increase the phonon energy. The peak emission cross section is 6 x 10(-21) cm(2) at 1537 nm and the fluorescence lifetime of the (4)I(13/2)-(4)I(15/2) transition is 4.1 ms. We have written 2-D channel waveguides in this glass using focused, 45-fs pulses from an amplified Ti:sapphire laser at different laser energies and writing speeds. Migration of atoms towards the periphery of the waveguides occurs, leading to refractive index changes. Channels show waveguiding at 1310 nm which is promising for the fabrication of integrated lasers and broadband amplifiers.

Energy pooling in multiple ionization and Coulomb explosion of clusters by nanosecond-long, megawatt laser pulses

We report the results of experiments that establish the possibility of bringing about multiple ionization and Coulomb explosion of molecular clusters with nanosecond laser pulses at intensities as small as 10(9) W cm(-2). We demonstrate several new facets of the laser-cluster interaction in the low-intensity, long-pulse domain: (i) The choice of laser wavelength for a given cluster species is very crucial. (ii) Excited electronic states play a very important role in the ionization dynamics. (iii) When field ionization is insignificant and ponderomotive energies are very small, it is energy pooling rather than inverse bremsstrahlung that determines how clusters absorb energy from the optical field.

Depolarization of white light generated by ultrashort laser pulses in optical media

We report measurements of the extinction ratio (ER) of white light generated upon irradiation of BK7 glass by ultrashort (36 fs) laser pulses with incident power approximately 10(3) times larger than the critical power for self-focusing. At low incident powers, the continuum is symmetric about the incident laser wavelength; at high powers it becomes broader and distinctly asymmetric towards the blue side. We observe that ER degrades by 100-fold after the onset of multiphoton-induced free-electron generation (at incident intensity approximately 2 TW cm-2), which also corresponds to the onset of asymmetry in white-light spectra.

Nonadiabatic response of molecules to strong fields of picosecond, femtosecond, and subfemtosecond duration: An experimental study of the methane dication

The double ionization of methane has been accomplished using strong optical fields that are generated using moderately intense lasers, and by strong fields that are induced by fast-moving, highly charged ions. In the former case laser intensities in the range 10(14) W cm(-2) generate fields whose durations are of 35 ps and 36 fs while in the latter case equivalent fields last for only 200-300 as. The dynamics of the field-ionized electrons are different in the two temporal regimes, fast (picoseconds), and ultrafast (few tens of femtoseconds and subfemtoseconds). Our experiments show that nonadiabatic effects come into play in the ultrafast regime; we directly monitor such effects by measuring the kinetic energy that is released when a specific bond in the doubly charged methane molecular ion breaks.

Euler buckling-induced folding and rotation of red blood cells in an optical trap

We investigate the physics of an optically driven micromotor of biological origin. When a single, live red blood cell (RBC) is placed in an optical trap, the normal biconcave disc shape of the cell is observed to fold into a rod-like shape. If the trapping laser beam is circularly polarized, the folded RBC rotates. A model based on geometric considerations, using the concept of buckling instabilities, captures the folding phenomenon; the rotation of the cell is rationalized using the Poincaré sphere. Our model predicts that (i) at a critical power of the trapping laser beam the RBC shape undergoes large fluctuations, and (ii) the torque that is generated is proportional to the power of the laser beam. These predictions are verified experimentally. We suggest a possible mechanism for the emergence of birefringent properties in the RBC in the folded state.

Efficient broadband emission from condensed media irradiated by low-intensity, unfocused, ultrashort laser light

We report here measurements of the efficiencies of broadband emission in different optical media using an unfocused, ultrashort (~40 fs) laser beam. Two different measurements have been carried out by placing a wire mesh in the path of the incident laser radiation. The wire mesh introduces a periodic intensity distribution in the x-y plane and also in the direction of the laser beam propagation. We measure both on-axis and offaxis components of the broadband emission and also observe modulation in broadband generation as the distance between the mesh and the sample is varied. The experimentally measured locations of broadband emission maxima are in agreement with simulations based on Fresnel diffraction integrals. The off-axis emission efficiencies lie in the range of 16-87%.

Optically-controllable, micron-sized motor based on live cells

We demonstrate rotation of live Chlamydomonas reinhardtii cells in an optical trap; the speed and direction of rotation are amenable to control by varying the optical trapping force. Cells rotate with a frequency of 60-100 rpm; functional flagella are shown to play a decisive role in rotation. The rotating cells generate torque (typically ~7500-12000 pN nm) that is much larger than that generated chemically by a dynein head in vitro (40 pN nm). The total force associated with a rotating live cell (~10 pN) suggests that activity of only a small fraction (~5%) of dynein molecules per beat cycle is sufficient to generate flagellar motion.

Strong light fields coax intramolecular reactions on femtosecond time scales

Energetic H(2) (+) ions are formed as a result of intramolecular rearrangement during fragmentation of linear alcohols (methanol, ethanol, propanol, hexanol, and dodecanol) induced by intense, pulsed optical fields. The laser intensity regime that is accessed in these experiments (peak intensity of 8 x 10(15) W cm(-2)) ensures multiple ionization of the irradiated alcohol molecules such that Coulomb explosions would be expected to dominate the overall fragmentation dynamics. Polarization dependent measurements show, counterintuitively, that rearrangement is induced by the strong optical field within a single, 100 fs long laser pulse, and that it occurs before Coulomb explosion of the field-ionized multiply charged alcohols.

Dissociative ionization of methane by chirped pulses of intense laser light

Measurements have been made of optical field-induced ionization and fragmentation of methane molecules at laser intensities in the 10(16) W cm(-2) range using near transform limited pulses of 100 fs duration as well as with chirped pulses whose temporal profiles extend up to 1500 fs. Data is taken both in constant-intensity and constant-energy modes. The temporal profile of the chirped laser pulse is found to affect the morphology of the fragmentation pattern that is measured. Besides, the sign of the chirp also affects the yield of fragments like C2+, H+, and H2+ that originate from methane dications that are formed by optical field-induced double ionization.

Highly efficient white light generation from barium fluoride

We demonstrate highly efficient white light generation by focusing 45 fs long pulses of 800 nm laser radiation with 1 mJ energy onto a 10 cm long barium fluoride crystal. The entire wavelength band from 400-1000 nm was generated with efficiency greater than 40%. We also observe multiphoton absorption induced fluorescence in the crystal. By employing line focusing geometry at low intensity, we show that white light fringes are formed with a single laser beam, indicative of the coherent property of the white light that is produced.

Burden of organochlorine pesticides in blood and its effect on thyroid hormones in women

Man has utilized a wide variety of pesticides to combat the crop pests and vectors of human diseases. However, in this process, he has overlooked the darker side of these noxious chemicals, the concentrations of which have reached the environment and pose serious threats, such as mutagenesis, teratogenesis, carcinogenesis and endocrine dysfunction in various components of the ecosystem. The present study was planned to assess the burden of organochlorine pesticides and their influence on thyroid function in women. The study included a total of 123 women from Jaipur City who visited the Thyroid clinic in SMS Medical College and Hospital. One hundred women showed normal thyroid hormone levels while the remaining 23 women had depleted T4 and high TSH levels. The qualitative and quantitative estimation of organochlorine pesticides was carried out by gas chromatography. Out of the analyzed pesticides, the concentration of p,p'-DDT and its metabolites was higher in all the subjects, but dieldrin was found to be significantly high in the hypothyroid women. The correlation analysis for dieldrin and depleted T4 levels in hypothyroid women elicited an inverse relationship between them.

Angiokeratoma of tongue

An 8-year-old male child who presented with lesions of angiokeratoma on tongue is described.

Asymmetric high-energy ion emission from argon clusters in intense laser fields

Clusters of 2x10(3) to 4x10(4) Ar atoms are Coulomb exploded in intense (up to 8x10(15) W cm(-2)) laser fields. The dependence of multiply charged argon ion energies on the polarization state of light is probed. A directional asymmetry in the ion-explosion energies is observed for the highest charge states. The ion-energy distribution consists of a low-energy isotropic component, and a high-energy anisotropic one. The results are discussed in terms of an asymmetric Coulomb-explosion scenario.

A statewide initiative to improve the care of hospitalized pneumonia patients: The Connecticut Pneumonia Pathway Project

PURPOSE

A statewide quality improvement initiative was conducted in Connecticut to improve process-of-care performance and to decrease length of stay for patients hospitalized with community-acquired pneumonia.

SETTING AND METHODS

Data were collected on 1,242 elderly (> or =65 years) pneumonia patients hospitalized at 31 of 32 acute care hospitals between January 16, 1995, and March 15, 1996, and on 1,146 patients hospitalized between January 1, 1997, and June 30, 1997. Interventions included feedback of performance data (Qualidigm, the Connecticut Peer Review Organization), dissemination of an evidence-based pneumonia critical pathway (Connecticut Thoracic Society), and sharing of pathway implementation experiences (hospitals). Process and outcome measures included early antibiotic administration, blood culture collection, oxygenation assessment, length of stay, 30-day mortality, and 30-day readmission rates. Analyses were adjusted for severity of illness and hospital-specific practice patterns.

RESULTS

After the statewide initiative, improvements were noted in antibiotic administration within 8 hours of hospital arrival (improvement from 83.4% to 88.8%, relative risk [RR] = 1.21; 95% confidence interval [CI]: 1.10 to 1.32), oxygenation assessment within 24 hours of hospital arrival (93.6% to 95.4%; RR = 1.23, 95% CI: 1.11 to 1.38), and length of stay (7 days to 5 days, P <0.001). There were no significant changes in blood culture collection within 24 hours of hospital arrival, blood culture collection before antibiotic administration, 30-day mortality, or 30-day readmission rates.

CONCLUSIONS

Statewide improvements were demonstrated in the care of hospitalized pneumonia patients concurrent with a multifaceted quality improvement intervention. Further research is needed to separate the effects of the quality improvement interventions from secular trends.

Thyroid hormone profile in obese subjects--a clinical study

Fifty obese subjects with body weight above 120% of the ideal weight for that height or body mass index greater than 27.8 kg/m2 in men or 27.3 kg/m2 in women were studied for thyroid hormone profile. Nearly three-fourths obese subjects had body mass index of 30-40 kg/m2. Eighty-six per cent subjects were clinically and biochemically euthyroid. Fourteen per cent of the subjects had hypothyroidism; out of them, 8% were clinically and biochemically hypothyroid while 6% were only biochemically hypothyroid. None of the hypothyroid subjects had morbid obesity (greater than 40 kg/m2 body mass index). Duration of obesity in hypothyroid subjects was less than 10 years in nearly three-fourths of cases.

Impact of systemic treatment on local control for patients with lymph node-negative breast cancer treated with breast-conservation therapy

PURPOSE

To determine the impact of tamoxifen and chemotherapy on local control for breast cancer patients treated with breast-conservation therapy.

PATIENTS AND METHODS

The data from 484 breast cancer patients who were treated with breast-conserving surgery and radiation were analyzed. Only patients with lymph node-negative disease were studied to provide comparative groups with a similar stage of disease and a similar competing risk for distant metastases. Actuarial local control rates of the 277 patients treated with systemic therapy (128, chemotherapy with or without tamoxifen; 149, tamoxifen alone) were compared with the rates for the 207 patients who received no systemic treatment. Only 10% of the patients had positive (2%), close (3%), or unknown margin status (5%).

RESULTS

Patients treated with systemic therapy had improved 5-year (97.5% v 89.8%) and 8-year (95.6% v 85.2%) local control rates compared with those that did not receive systemic treatment (P =.004, log-rank test). There was no statistical difference in local control between patients treated with chemotherapy and patients treated with tamoxifen alone (P =.219). Systemic treatment, margin status, young patient age, estrogen and progesterone receptor status, and primary tumor size were analyzed in a Cox regression analysis. The use of systemic treatment was the most powerful predictor of local control: patients who did not receive systemic treatment had a relative risk of local recurrence of 3.3 (95% confidence interval, 1.5 to 7.5; P =.004).

CONCLUSION

In this retrospective analysis, systemic therapy appears to contribute to long-term local control in patients with lymph node-negative breast cancer treated with breast-conservation therapy.