We present the key elements required for continuous variable parallel quantum information protocols based on spatial multimode quantum correlations. We describe techniques for encoding, combining and ...detecting spatial quantum information with high efficiency in the individual transverse modes. Until now, the missing feature for the implementation of such protocols was the generation of squeezing in higher order transverse Hermite-Gauss modes. We experimentally demonstrate squeezing in selective modes by fine-tuning the phase matching condition of the nonlinear chi(2) material and the cavity resonance condition of an optical parametric amplifier. Combined, these results open the way to practical multimode optical quantum information systems.
We present highly efficient sum-frequency generation between two CW IR lasers using periodically poled KTP. The system is based on the 1064 and 1342 nm laser-lines of two Nd:YVO4 lasers. This is an ...all solid-state light source in the yellow-orange spectral range. The system is optimized in terms of efficiency as well as stability. We compare the performance of a singly and a doubly resonant system, and find that the stability of the singly resonant system is superior to that of the doubly resonant system. We find that the overall conversion efficiency of the single resonant system is higher than for the doubly resonant configuration.
Disease-modifying treatment strategies for Alzheimer's disease have led to an urgent need for biomarkers to identify the disease at a very early stage. Here, we assess the association between CSF ...biomarkers and incipient Alzheimer's in patients with mild cognitive impairment (MCI).
From a series of 180 consecutive patients with MCI, we assessed 137 who underwent successful lumbar puncture at baseline. Patients at risk of developing dementia were followed clinically for 4–6 years. Additionally, 39 healthy individuals, cognitively stable over 3 years, served as controls. We analysed CSF concentrations of β amyloid
1–42 (Aβ42), total tau (T-tau), and phosphorylated tau (P-tau
181) using Luminex xMAP technology.
During follow-up, 57 (42%) patients with MCI developed Alzheimer's disease, 21 (15%) developed other forms of dementia, and 56 (41%) remained cognitively stable for 5·2 years (range 4·0–6·8). A combination of CSF T-tau and Aβ42 at baseline yielded a sensitivity of 95% and a specificity of 83% for detection of incipient AD in patients with MCI. The relative risk of progression to Alzheimer's disease was substantially increased in patients with MCI who had pathological concentrations of T-tau and Aβ42 at baseline (hazard ratio 17·7, p<0·0001). The association between pathological CSF and progression to Alzheimer's disease was much stronger than, and independent of, established risk factors including age, sex, education,
APOE genotype, and plasma homocysteine. The combination of T-tau and Aβ42/P-tau
181 ratio yielded closely similar results (sensitivity 95%, specificity 87%, hazard ratio 19·8).
Concentrations of T-tau, P-tau
181, and Aβ42 in CSF are strongly associated with future development of Alzheimer's disease in patients with MCI.
Phasematch curves as well as sensitivity to angular and wavelength misalignment for generation of second-harmonic of 785 nm and 810 nm in Bi(3)BO(6) crystal was calculated. Measurements were done for ...intra-cavity CW SHG in a Ti:Sapphire laser. The BiBO crystal was found to be excellent for this application. Temperature dependance was uncritical for both crystals, while power stability was good. Maximum blue output was 53 mW at 392 nm and 100 mW at 405 nm; corresponding to pump-to-blue optical conversion efficiencies of 0.96% and 1.82% respectively.
In this paper the results of a theoretical and experimental investigation of synchronized passive Q-switching of two Nd:YVO4-based solid-state lasers operating at two different wavelengths, is ...described. A V:YAG saturable absorbing material was used as a passive Q-switch performing the synchronization of the two laser fields. This material provides Q-switching operation at both 1064 and 1342nm wavelengths simultaneously, saturating the same energy level. By adjusting the pump power of both lasers, it was possible to optimize the overlap of the two pulse trains and to switch between different states of synchronization. A theoretical model based on rate equations, which has been developed in order to investigate optical performance of the laser system, is in a good agreement with the experimental results. The principle of synchronized Q-switching can lead to new, pulsed all-solid-state light sources at new wavelengths based on sum-frequency mixing processes.
Identifying individuals at high risk of developing Alzheimer's disease (AD) is important for future therapeutic strategies, and there is a clinical need for diagnostic biomarkers to identify ...incipient AD.
The aim of the present study was to investigate if the AD-associated Abeta peptide pattern recently found in cerebrospinal fluid (CSF) could discriminate between patients with incipient AD and those with stable mild cognitive impairment (MCI) by analyzing CSF from patients with MCI at baseline.
The levels of Abeta(1-37, -38, -39, -40, -42) were analyzed by Abeta-SDS-PAGE/immunoblot in CSF from 19 healthy controls, 25 patients with stable MCI and from 25 patients with MCI who later developed AD during 4- to 6-year follow-up.
All healthy controls and 20 out of 22 patients who developed AD were correctly classified by their baseline Abeta peptide pattern. In 9 out of 25 stable MCI patients, the pattern indicated incipient AD in spite of clinical nonconversion. Interestingly, these individuals had apolipoprotein E genotypes and CSF levels of tau and phospho-tau that are known to be associated with high risk of AD.
Altogether, our study reveals the novel finding that the Abeta peptide pattern is able to predict AD in patients with MCI with a sensitivity of 91% and specificity of 64%. The specificity would increase to 94% if the high-risk patients in the stable MCI cohort developed AD during extended follow-up.
The CSF biomarkers tau and Abeta42 can identify patients with AD, even during the preclinical stages. However, previous studies on longitudinal changes of tau and Abeta42 in individual patients with ...AD and elderly controls report somewhat inconsistent results.
We investigated the levels of tau and Abeta42 at baseline and after 1 year in 100 patients with AD. In a second cohort of 45 AD patients we measured the CSF biomarkers at baseline and after 2 years. Moreover, in 34 healthy elderly controls the CSF biomarkers were followed for 4 years. The baseline levels of tau were increased with >60% in AD patients compared to controls (p<0.001), while baseline Abeta42 levels were decreased with >50% (p<0.001). In the AD group followed for 2 years, tau increased with 16% compared to the baseline levels (p<0.05). However, the levels of tau were stable over 4 years in the controls. The levels of Abeta42 did not change significantly over time in any of the groups. In the patients with AD, tau was moderately associated with worse cognitive performance already at baseline (p<0.05).
Tau and Abeta42 in CSF seem to reflect the underlying disease state in both early and late stages of AD. The slight increase in tau over time observed in the patients with AD is modest when compared to the relatively large difference in absolute tau levels between AD patients and controls. Therefore, these markers maintain their usefulness as state markers over time and might serve as surrogate markers for treatment efficacy in clinical trials.
Aim. To study possible detrimental maternal and neonatal effects of immersion in warm water during labor.
Design. Prospective randomized controlled bathing during first stage of labor vs no bathing.
...Setting. Obstetrical departments at a university hospital and two central hospitals.
Primary end‐point. Referral of newborns to NICU.
Material and methods. Randomization took place by means of sealed opaque envelopes at each delivery unit. Preconditions for participation in the study were: singleton parturient wishing to bathe, a gestational duration of at least 35 weeks+0 days, a planned vaginal delivery, normal admission test, regular contractions and cervix dilated to at least 3–4 cm. Parturients randomized to the ‘no bath’ control group were allowed to use a shower. Rupture of the membranes was not a contra‐indication to participation. Those excluded from randomization were women with intra‐uterine growth retardation, meconium‐stained amniotic fluid, or in the event that the tub was occupied by another randomized parturient.
Main results. On average, parturients stayed in the tub for 50–60 min. No significant difference was seen regarding the referral rate to NICU among 612 cases vs 625 controls, OR 0.8; 95% CL 0.2, 3.1. The OR for epidural analgesia was 1.0; 95% CL 0.8, 1.3. Nor was any significant difference seen in the rate of perineal tear grade III–IV (OR 1.3), instrumental delivery (OR 1.1), cesarean section (OR 1.8), or maternal post partum stay on the ward. During the neonatal period, no significant difference was seen in the number of newborns with Apgar <7 at 5 min (4 vs 5), neonatal distress (OR 2.2) or tachypnéa (OR 1.0).
Conclusion. In the present study no negative effects of bathing during labor could be discerned. The results indicate that expectant mothers wishing to bathe during labor may do so without jeopardizing their own, or their newborns’ wellbeing after birth.
The material V:YAG can work as a saturable absorber both at 1064 and 1342 nm. It is shown in this paper, that the saturation effect is spectrally homogeneous. V:YAG can therefore be used for ...generation of passively synchronized Q-switched pulses at wavelengths hundreds of nanometers apart. First a pump–probe experiment is described, investigating the fundamental cross wavelength coupling. Then the first measurements of synchronized Q-switched pulses using a solid-state passive saturable absorber are presented. Finally a setup containing two different saturable absorbing materials is investigated, showing very stable passive synchronized Q-switching at two distinct wavelengths.
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