Moderate Compression Research Articles

Failure limits of continuous carbon fibre reinforced plastics loaded with fibre parallel compression

Abstract The strength analysis of continuous fibre reinforced plastics has to consider the reactions of the heterogeneous composite material. Ample uncertainties exist in the evaluation of fibre parallel compressive load, because no computation model has yet accomplished acceptance which on the one hand is physically fundamentally feasible and on the other hand works on the macroscopical level of the common design process. This paper deals with the combination of a physically based failure model and a suitable modelling of the complex elastic properties. The results of this model combination are overall plausible. Additionally, experimental data confirm that moderate fibre transverse compression leads to an increase in the fibre parallel compressive strength.

Combining Structural and Electrochemical Analysis of Electrodes Using Micro-Computed Tomography and a Microfluidic Fuel Cell

Detailed investigation of the relationship between the physical structure and electrochemical activity of state-of-the-art fuel cell electrodes is a critical, yet often poorly reported or proprietary, step in the manufacturing of cheaper and more durable configurations. Here we demonstrate the utility of X-ray micro-computed tomography (MicroCT) for detailed characterization of the architecture and buried interfaces of fuel cell electrodes in a non-destructive fashion. We employ a combined thresholding and filament tracing based analytical protocol for image analysis which enables more accurate quantification of GDE structures as compared to previously-used thresholding-only methods. Furthermore, we report on a methodology of combining in-situ electrochemical analysis in a microfluidic fuel cell and ex-situ structural analysis in a MicroCT which enables direct correlation of changes in electrode performance to changes in physical structure, in this case, porosity. As a demonstration, the effects of electrode compression are investigated. We observed that both subtle shifts in structure in the microporous and catalyst layers at low compression pressures (<1 × 103 lbf) and more drastic structural densification of the macroporous carbon fiber layer at moderate compression pressures (≥1 × 103 lbf) impact electrode performance.

A Cloak Scheme Insusceptible to the Change of Material Properties

An electromagnetic cloak based on a coordinate transformation approach is always inhomogeneous and anisotropic. In this paper, we investigate the sensitiveness of different cloaking schemes, when EM parameters are limited to a range more plausible to realize. Numerical experiments show that the imperfect cloak under moderate compression presents low anisotropy and is a candidate scheme more insusceptible to changes in EM parameters. When devising the cloak using dispersive lossy metamaterials, the unavoidable deviation in material parameters favors a lower anisotropic model such as the imperfect cloaking model.

Stabilization of Juxta‐Physeal Distal Tibial and Fibular Fractures in a Juvenile Tiger Using a Hybrid Circular–Linear External Fixator

To report stabilization of closed, comminuted distal metaphyseal transverse fractures of the left tibia and fibula in a tiger using a hybrid circular-linear external skeletal fixator. Clinical report. Juvenile tiger (15 months, 90 kg). From imaging studies, the tiger had comminuted distal metaphyseal transverse fractures of the left tibia and fibula, with mild caudolateral displacement and moderate compression. Multiple fissures extended from the fractures through the distal metaphyses, extending toward, but not involving the distal tibial and fibular physes. A hybrid circular-linear external skeletal fixator was applied by closed reduction, to stabilize the fractures. The fractures healed and the fixator was removed 5 weeks after stabilization. Limb length and alignment were similar to the normal contralateral limb at hospital discharge, 8 weeks after surgery. Two weeks later, the tiger had fractures of the right tibia and fibula and was euthanatized. Necropsy confirmed pathologic fractures ascribed to copper deficiency. Closed application of the hybrid construct provided sufficient stability to allow this 90 kg tiger's juxta-articular fractures to heal with minimal complications and without disrupting growth from the adjacent physes.

Dietary niche partitioning in a piscivorous fish guild in response to stocking of an additional competitor – The role of diet specialisation

Species belonging to the same ecological guild can coexist only if there are differences in their responses to limiting resources. Thus, competitor introductions may modify the niches of the resident competitors, but empirical studies are rare. The extent of niche modification might further depend on the species’ trophic specialisation along the specialists-to-generalists axis. In this study, we performed a semi-natural experiment by introducing a trophically specialised piscivorous fish (pikeperch) to the resident predator guild of a trophic generalist (perch) and a trophic specialist (pike) in a temperate freshwater lake. Individual diet data were used to calculate total niche hypervolume and inter- and intraspecific dietary niche overlap to evaluate strength of competitive interactions before and after pikeperch introduction. In both pike and perch, there was a moderate niche compression in response to pikeperch stocking. Furthermore, whereas perch diet hypervolume did not overlap at all with that of pikeperch, the intersection of niche space between the two trophic specialists was highly asymmetrical in favour of pike due to its less specialised diet composition in comparison with pikeperch. The intraspecific dietary niche overlap between perch size classes reflected an enhanced partitioning, whereas that of pike size classes was found almost unchanged in response to pikeperch stocking. These empirical results corroborate that competitive interactions and the degree of specialisation may strongly shape the success of introductions of top-predators in freshwater ecosystems. The most specialised species may persist only if the competitors belong rather to the generalists along the specialisation continuum.

CD11d integrin blockade reduces the systemic inflammatory response syndrome after spinal cord injury

Traumatic injury to the spinal cord triggers a systemic inflammatory response syndrome (SIRS), in which inflammatory cells from the circulation invade organs such as the liver, lung and kidney, leading to damage of these organs. Our previous study (Gris, et al, Exp. Neurol, 2008) demonstrated that spinal cord injury (SCI) activates circulating neutrophils that then invade the lung and kidney from 2 to 24 h after injury, increasing myeloperoxidase activity, cyclooxygenase-2 and matrix metalloproteinase-9 expression and lipid peroxidation in these organs. The present study was designed to ascertain whether a treatment that limits the influx of leukocytes into the injured spinal cord would also be effective in reducing the SIRS after SCI. This treatment is intravenous delivery of a monoclonal antibody (mAb) against the CD11d subunit of the CD11d/CD18 integrin expressed by neutrophils and monocytes. We delivered the anti-CD11d mAb at 2 h post moderate clip compression SCI at the 4th or 12th thoracic segments and assessed inflammation, oxidative activity and cellular damage within the lung, kidney and liver at 12 h post-injury. In some analyses we compared high and low thoracic injuries to evaluate the importance of injury level on the intensity of the SIRS. After T4 injury, treatment with the anti-integrin mAb reduced the presence of neutrophils and macrophages in the lung, with associated decreases in expression of NF-κB and oxidative enzymes and in the concentration of free radicals in this organ. The treatment also reduced lipid peroxidation, protein nitration and cell death in the lung. The anti-CD11d treatment also reduced the inflammatory cells within the kidney after T4 injury, as well as the free radical concentration and amount of lipid peroxidation. In the liver, the mAb treatment reduced the influx of neutrophils but most of the other measures examined were unaffected by SCI. The inflammatory responses within the lung and kidney were often greater after T4 than T12 injury. Clinical studies show that SIRS, with its associated organ failure, contributes significantly to the morbidity and mortality of SCI patients. This anti-integrin treatment may block the onset of SIRS after SCI.

Large Hadron Collider reach for supersymmetric models with compressed mass spectra

Many theoretical and experimental results on the reach of the Large Hadron Collider are based on the mSUGRA-inspired scenario with universal soft supersymmetry breaking parameters at the apparent gauge coupling unification scale. We study signals for supersymmetric models in which the sparticle mass range is compressed compared to mSUGRA, using cuts like those employed by ATLAS for 2010 data. The acceptance and the cross-section times acceptance are found for several model lines that employ a compression parameter to smoothly interpolate between the mSUGRA case and the extreme case of degenerate gaugino masses at the weak scale. For models with moderate compression, the reach is not much worse, and can even be substantially better, than the mSUGRA case. For very compressed mass spectra, the acceptances are drastically reduced, especially when a more stringent effective mass cut is chosen.

Protective effect of caspase inhibition on compression‐induced muscle damage

There are currently no effective therapies for treating pressure-induced deep tissue injury. This study tested the efficacy of pharmacological inhibition of caspase in preventing muscle damage following sustained moderate compression. Adult Sprague-Dawley rats were subjected to prolonged moderate compression. Static pressure of 100 mm Hg compression was applied to an area of 1.5 cm2 in the tibialis region of the right limb of the rats for 6 h each day for two consecutive days. The left uncompressed limb served as intra-animal control. Rats were randomized to receive either vehicle (DMSO) as control treatment (n =8) or 6 mg kg⁻¹ of caspase inhibitor (z-VAD-fmk; n =8) prior to the 6 h compression on the two consecutive days.Muscle tissues directly underneath the compression region of the compressed limb and the same region of control limb were harvested after the compression procedure.Histological examination and biochemical/molecular measurement of apoptosis and autophagy were performed. Caspase inhibition was effective in alleviating the compression-induced pathohistology of muscle. The increases in caspase-3 protease activity, TUNEL index, apoptotic DNA fragmentation and pro-apoptotic factors (Bax, p53 and EndoG) and the decreases in anti-apoptotic factors (XIAP and HSP70) observed in compressed muscle of DMSO-treated animals were not found in animals treated with caspase inhibitor. The mRNA content of autophagic factors (Beclin-1, Atg5 and Atg12) and the protein content of LC3, FoxO3 and phospho-FoxO3 that were down-regulated in compressed muscle of DMSO-treated animals were all maintained at their basal level in the caspase inhibitor treated animals. Our data provide evidence that caspase inhibition attenuates compression-induced muscle apoptosis and maintains the basal autophagy level. These findings demonstrate that pharmacological inhibition of caspase/apoptosis is effective in alleviating muscle damage as induced by prolonged compression.

Application of detector precision characteristics and histogram packing for compression of biological fluorescence micrographs

Modern applications of biological microscopy such as high-content screening (HCS), 4D imaging, and multispectral imaging may involve collection of thousands of images in every experiment making efficient image-compression techniques necessary. Reversible compression algorithms, when used with biological micrographs, provide only a moderate compression ratio, while irreversible techniques obtain better ratios at the cost of removing some information from images and introducing artifacts. We construct a model of noise, which is a function of signal in the imaging system. In the next step insignificant intensity levels are discarded using intensity binning. The resultant images, characterized by sparse intensity histograms, are coded reversibly. We evaluate compression efficiency of combined reversible coding and intensity depth-reduction using single-channel 12-bit light micrographs of several subcellular structures. We apply local and global measures of intensity distribution to estimate maximum distortions introduced by the proposed algorithm. We demonstrate that the algorithm provides efficient compression and does not introduce significant changes to biological micrographs. The algorithm preserves information content of these images and therefore offers better fidelity than standard irreversible compression method JPEG2000.

Spinal Epidermoid Cyst in a SJL Mouse: Case Report and Literature Review

This report is the first description of a spinal epidermoid cyst (EC) in a SJL mouse and gives an overview on the occurrence of ECs in animals including dogs, horses, mice and rats. The EC was not detected grossly and the mouse did not display clinical signs or an altered rotarod performance. Microscopically, there was an oval cyst lined by stratified squamous epithelium that was attached to the dorsolateral meninges and caused moderate compression of the adjacent lumbar spinal cord. ECs in mice and rats are mainly located in the caudal part of the spinal cord with a variable, strain-dependent occurrence. ECs in mice and rats are not associated with clinical signs and can be interpreted as incidental findings.

Mechanical and corrosion properties of binary Mg–Dy alloys for medical applications

Abstract Microstructure, mechanical and corrosion properties of binary magnesium–dysprosium (Mg-5, 10, 15, 20 wt.% Dy) alloys were investigated for medical applications. In the as-cast condition, the distribution of Dy is quite inhomogeneous. Mg–10Dy alloy exhibits a moderate tensile and compression yield strength, and the best elongation and corrosion resistance. After T4 (solutionizing) treatment, the distribution of Dy becomes homogeneous. The tensile and compression yield strength of all Mg–Dy alloys decreases. The elongation remains unchanged, while the corrosion resistance is largely improved after T4 treatment.

Opposing responses of apoptosis and autophagy to moderate compression in skeletal muscle

The molecular mechanism that contributes to the pathogenesis of deep pressure ulcer remains to be elucidated. This study tested the hypotheses that: (1) apoptosis and autophagy are activated in compression-induced muscle pathology and (2) apoptotic and autophagic changes precede pathohistological changes in skeletal muscle in response to prolonged moderate compression. Adult Sprague-Dawley rats were subjected to an experimental model of pressure-induced deep tissue injury. Static pressure of 100 mmHg was applied to an area of 1.5 cm(2) over the mid-tibialis region of right limb of rats for one single session of 6-h compression (1D) or two sessions of 6-h compression over two consecutive days with rats sacrificed one day (2D) or immediately after (2D-IM) the compression. The left uncompressed limb served as the intra-animal control. Muscle tissues underneath compression region were collected for analysis. Our histological analysis indicated that pathohistological characteristics including rounding contour of myofibres and massive nuclei accumulation were apparently demonstrated in muscles of 2D and 2D-IM. In contrast, these pathohistological changes were generally not found in muscle following 1D. Apoptotic DNA fragmentation, terminal dUTP nick-end labelling index and caspase-3 protease activity were significantly elevated in compressed muscles of all groups. Caspase-9 enzymatic activity was found to be significantly increased in compressed muscles of 2D and 2D-IM whereas increase in caspase-8 activity was exclusively found in compressed muscle of 1D. According to our immunoblot analysis, FoxO3 was significantly reduced in compressed muscles of all groups whereas Beclin-1 was decreased only in 2D. LC3-I was significantly reduced in compressed muscles of all groups while LC3-II was decreased in 2D and 1D. No significant differences were found in the protein abundance of Akt and phospho-Akt in muscles among all groups. These data demonstrate the opposing responses of apoptosis and autophagy to moderate compression in muscle. Moreover, our findings suggest that cellular changes in apoptosis and autophagy have already taken place in the very early stage in which apparent histopathology has yet to develop in the process of compression-induced muscle pathology.

外部圧迫による筋血流量の変化が低強度運動時の筋放電量と最大筋力に及ぼす影響

It has been reported that low-intensity exercise training with restriction of muscular blood flow (LI-BFR) results in a significant increase of muscle size and strength, although the mechanisms of BFR-induced muscle adaptation are still poorly understood. Changes in muscle activation level during a BFR exercise session may be an important factor for improvement of muscle size and function. However, the relationship between the actual level of induced blood flow restriction and muscle stimulated during the exercise has not yet been explored. The purpose of this study was to investigate the relationship between muscle activation level evaluated by electromyography (EMG) and muscular blood flow or muscle fatigue during low-intensity resistance exercise with and without BFR. Ten young men participated in three experimental trials: exercise without BFR (CON), exercise with moderate external compression (1.4×systolic arterial pressure, BFR-L), and exercise with high external compression (1.8×systolic arterial pressure, BFR-H). Each subject performed low-intensity (20% of one repetition maximum, 1RM) knee extension exercise (30 reps followed by 3 sets of 15 reps, with a 30-s rest between sets). Maximum voluntary isometric strength (MVC) and thigh muscle blood flow were measured before and immediately after each exercise session. Surface EMG was recorded from the quadriceps muscle (vastus lateralis and vastus medialis) during the exercise session, and the integrated EMG (iEMG) was calculated. iEMG increased gradually during each exercise session in all three trials, and the relative increase in iEMG tended to be greater in BFR-H (P=0.07). Decreases in MVC were associated with the magnitude of external compression (CON: −3%, BFR-L: −13%, BFR-H: −25%), and significant differences were found between CON and BFR-L or BFR-H and between BFR-L and BFR-H. Significant positive correlations were observed between changes in MVC and iEMG (r=0.49, P<0.01) and between changes in MVC and muscle blood flow (r=0.56; P<0.01). Our results indicate that BFR-induced increases in muscle activation are correlated with decreased muscle blood flow resulting from external compression and the level of muscle fatigue.

“Correlation of Magnetic Resonance Patterns of Lumbar Disc Disease with Clinical Symptomatology of Patientsâ€

Objective: To describe the patterns of degenerative changes in lumbar spine discs in correlation with cli-nical symptomatology of patients. Patients and Methods: This cross sectional analy-tical study was carried out in Radiology Department of Children Hospital Lahore, from October 2006 to Octo-ber 2007. The study included 170 patients who presen-ted with low back and leg pain. All patients underwent lumbar MRI using 1.5 T - scanner. MRI scans were evaluated for magnitude and location of nerve com-pression, disc bulge or disc herniation and the nature of nerve and thecal sac deformation and association of these findings with age, sex and clinical symptomato-logy of patients was evaluated. Results: The study included 170 patients, the age range was 20 to 79 years (mean 47 years). Disc bulge was most frequent finding seen in 128 patients (74%), disc herniation was seen in 42 patients (25%) and was common in patient with acute history of backache, while disc bulge was common in patients with chronic symptoms. Overall 131 patients (76%) had MRI evi-dence of nerve or thecal sac compression. There was no significant association between segmental distribu-tion of symptoms and presence of anatomic impair-ment. However, severe nerve compression and disc herniation were significantly associated with pain dis-tal to the knees. Conclusion: The presence of disc herniation or ipsi-lateral severe nerve compression at one or multiple sites is strongly associated with distal leg pain and sen-sory symptoms in that leg. Mild to moderate nerve compression, disc degeneration or bulging, and non disc degenerative changes are not significantly associ-ated with specific pain patterns.

Interparticle distance in monolayers controlled by soft spacers

This paper addresses the use of graft polymer layers as spacers to control interparticle distance in 2-dimensional monolayers. Gold nanoparticles grafted with thermosensitive PNIPAM-based polymers with a large range of molecular mass and different degrees of hydrophobicity have been studied. The hydrophobicity of the polymer is adjusted by incorporation of a comonomer n-propylamine. The resulting copolymer, PNIPAM-co-NPAM, exhibits lower collapse transition temperature and increased cooperativity in the collapse process with n ≈ 150 compared to n ≈ 100 for PNIPAM, n being the number of monomers per collapse domain. Langmuir isotherms of these polymers under moderate compression follow closely a π ≈ c3 behavior with corresponding critical exponent ν = 3/4 as predicted for 2-dimensional polymer conformation in good solvent. Nanoparticles grafted with these polymers form stable Langmuir monolayers where the graft polymer chains adopt a 2-D stretched conformation that tethers the nanoparticles to the interface. The nanoparticle cores are thus isolated by the polymer shells resulting in nanoparticle areas that increase with polymer chain length. Correspondingly, the interparticle distance is found to vary with chain length as Dp ≈ N0.8. For the Au-PNIPAM-NPAM, a moderate increase in temperature to near-θ conditions decreases the nanoparticle area by about 30% through lateral collapse of the polymer layer. This thermally induced molecular collapse in a 2-D monolayer is an unusual and novel observation that may be attributed to cooperative effects of the collapse transition of the new copolymer PNIPAM-co-NPAM.

Asymptomatic Cervical Cord Compression in Lumbar Spinal Stenosis Patients

A retrospective study. To analyze incidence of asymptomatic cervical cord compression and related factors in lumbar stenosis patients. Neural compression resulted from degenerative disc is not unusual in the asymptomatic cervical spine. However, its incidence and clinically related factors in lumbar stenosis patients have not been studied. We analyzed lumbar stenosis index (LSI), cervical cord compression index (CCI), and Torg-Pavlov ratio of whole spine magnetic resonance images of 93 lumbar stenosis patients. We compared lumbar stenosis involving a single segment versus multiple segments in the cases with the LSI of double-level or more, patients in 60s versus in 70s, and male versus female for the above variables. Of total 93 cases, 71 cases did not demonstrate cervical cord compression, but moderate or severe cervical cord compression was observed in 22 cases (23.7%). The multiple segment lumbar stenosis group, the 70s group, and male group had statistically significant higher CCI. The correlation coefficient between the CCI and the LSI indicated a strong positive linear relationship with 0.54 (P = 0). Moderate or severe cervical cord compression was observed in 24% of lumbar stenosis patients. Asymptomatic cervical cord compression is more likely to be developed in lumbar stenosis patients who are aged, male, and involving multiple segments. These factors should be considered for management of lumbar stenosis patients.

Comparative Study of the Effect of Lossy and Lossless Block Based Binary Plane Techniques on Medical Images

Problem statement: The general and medical images in specific contain different regions holding information of different significances. To elaborate medical information, the doctor prefers t o focus on certain selected region (s) of interest. S o for medical images the diagnostically important regions must be preserved at high quality, whereas the rest of the image is required only in a context ual sense. In this context, the study of compression technique s needed to maintain quality in reconstructed image. Approach: This study proposed the Lossless and lossy block ba sed binary plane techniques and implemented on different medical images with respect to compression rate and quality. This technique divides the image into blocks of 3◊3 size before the main process is started. At the edges i f the block is not of 3◊3 dummy rows and columns are added to make the block suitable for processing. Results: The proposed the Lossless Block Based Binary Plane Technique is to reconstruct the chestx- ray.raw image with 100%, no loss and it achieves moderate compression rate. The lossy Block Based Binary Plane Technique compresses the image with high compression rate. The loss in this technique can be controlled by varying the threshold value to have compromise between the compression rate and quality in reconstructed image. The results are compared with popular compression technique i.e JPEG. Conclusion/Recommendations: This technique can be applied for region based com pression of image. The region with significant information can be applied with Loss Less Block Based Binary Plane. The regions with insignificant information c an be applied with lossy Technique to achieve more compression. This technique also extended for color images with few modifications.

Correlation of MR tomographic findings and microvascular decompression treatment of the neurovascular compressions of the cranial nerves

Objective To explore the correlation of the operation effects of the miorovascular decompression(MVD) and the findings on magnetic resonance tomographic angiography(MRTA) in patients of neurovascular compression of the cranial nerves.Methods Two hundred and twenty three patients treated with the microvascular decompression were analyzed retrospectively.They were grouped and graded according to the vessel compression on the cranial nerves.The compression were grouped as none, moderate and severe, and the operation effects were graded as Ⅰ ( complete relief), Ⅱ ( partial relief) and Ⅲ ( no relief).The operation effects grades were correlated according to the compression groups by Kruskal-Wallis test and the operation effects between each two of the groups were compared using Nemenyi test.P < 0.05 was defined as statistic significant.Results Of the 53 cases of non-compression group, 31 cases were graded as Ⅰ , 13 cases were graded as Ⅱ and 9 cases were graded as Ⅲ, according to the operation-effects of the decompression.Of the 110 cases of moderate group,95 cases were grade as Ⅰ , 11 cases were graded as Ⅱ and 4 cases were graded as Ⅲ.Of the 60 cases of severe group, 48 cases were graded as Ⅰ, 7 cases were graded as Ⅱ and 5 cases were graded as Ⅲ.There were statistic significance among the three groups,where χ2= 16.84 and P <0.05.The mean rank of the non-compression, the moderate and the severe group was 134.21,102.37 and 110.4 ,respectively.The difference of the mean ranks between the non-compression group and the moderate group was 31.84, and between the non-compression and the severe group was 24.17, respectively, where P < 0.05 both.Conclusions There was close relationship between the findings on magnetic resonance tomographic angiography and the operation effects of the MVD.The operation effects of patients with moderate and severe vessel compression were much better than the non-compression group.MRTA is helpful for MVD surgical indication and its prognosis. Key words: Trigeminal neuralgia; Decompression,surgical ; Magnetic resonance imaging

Deformation twinning in Ti-6Al-4 V during low strain rate deformation to moderate strains at room temperature

This study examines the possibility of twinning to occur in Ti-6Al-4 V during moderate (4 - 14%) uniaxial compression at room temperature using a slow strain rate (10 −6s −1). To do this, the starting material was manufactured to have strong basal texture components in the transverse and normal directions but not in the rolling direction. After only 6% compressive deformation parallel to the rolling direction it was possible to indentify a significant texture change introducing a strong basal texture component in the rolling direction. TEM analysis provided evidence of twins within grains, but at too low a volume fraction to explain the texture changes. Detailed EBSD mapping was carried out and showed an increasing number of entire grains to have their c-axis aligned with the loading direction in the deformed material, suggestive of entire grain twinning. The root cause for sudden complete grain twinning can only be speculated about at the moment, but it is suggested that the stress required for twin nucleation is significantly higher than that required for their propagation.

Type-I cascaded quadratic soliton compression in lithium niobate: Compressing femtosecond pulses from high-power fiber lasers

The output pulses of a commercial high-power femtosecond fiber laser or amplifier are typically around 300-500 fs with a wavelength around 1030 nm and 10s of $\mu$J pulse energy. Here we present a numerical study of cascaded quadratic soliton compression of such pulses in LiNbO$_3$ using a type I phase matching configuration. We find that because of competing cubic material nonlinearities compression can only occur in the nonstationary regime, where group-velocity mismatch induced Raman-like nonlocal effects prevent compression to below 100 fs. However, the strong group velocity dispersion implies that the pulses can achieve moderate compression to sub-130 fs duration in available crystal lengths. Most of the pulse energy is conserved because the compression is moderate. The effects of diffraction and spatial walk-off is addressed, and in particular the latter could become an issue when compressing in such long crystals (around 10 cm long). We finally show that the second harmonic contains a short pulse locked to the pump and a long multi-ps red-shifted detrimental component. The latter is caused by the nonlocal effects in the nonstationary regime, but because it is strongly red-shifted to a position that can be predicted, we show that it can be removed using a bandpass filter, leaving a sub-100 fs visible component at $\lambda=515$ nm with excellent pulse quality.