Weak back

Signs and Symptoms Initial symptoms include fever, generalized weakness, back pain, dizziness, and extreme weight loss. There may also be occasional nausea and vomiting. Fever may be biphasic. In some cases the illness can become hemorrhagic or cause inflammation of the brain leading to headaches, coma, or seizures. Can also cause inflammation of the eyes with an intolerance to light. Up to 10% of affected patients may have some permanent vision loss. 

We may expect that the future will see many additional uses of cationic zirconocenes in organic synthesis, in which their Lewis acidic character, coupled with the special properties of zirconium (oxophilic, fluorophilic) and its d°-electron configuration (leading, for example, to weak back-bonding) will come into play. 

The M-N-N-M moiety in these complexes could be linear, M( n -N2)M, (for weak back donation interaction) or zigzag, or even rhombic, M(t 2-N2)M, depending on the strength of the 7i-back donation (see Figure 1). 

This fast removal of Si-F species can be ascribed to the weakening of the Si backbonds induced by the strong polarizing effect of F [Ubl], The weak back-bonds are then attacked by HF or H20. This reaction scheme for the dissolution process is supported by quantum-chemical calculations [Trl]. The observed dissolution valence of two for Jelectron injection current and Si-F bond density [Be22] are experimental findings that are in support of the divalent dissolution mechanism, as shown in Fig. 4.3 [Lei, Ge7, Ho6]. 

Fig. 6. Lower part angular dependence of the non-normalized static scattering intensity I(q) observerd with latex particles (R=265 nm). Upper part dependence of r/q =D on the scattering angle in dynamic LS. The sharp downturn at large scattering angles results from a weak back reflection of light on the boundary of the aqueous solution to the index matching bath, that consisted of toluene. This reflection results from the difference in the refractive indices of water (n = 1.333) and toluene (n =1.51). Reprinted with permission from [182]. Copyright [1982] American Society...

Myalgia, asthenia or unusual fatigue and weakness, back pain Serious Reactions... 

These two herbs are warm in nature and enter the Kidney meridian directly. They are able to tonify the Kidney-Yang. They have a strong point of strengthening the bones, and are often selected to treat a cold and weak back and limbs. Du Zhong is also able to tonify the Kidney, calm the fetus and prevent habitual miscarriage. 

Thiazolidinediones Pioglitazone (Actos) Rosiglitazone (Avandia) Similar to the biguanides (metformin) Headache dizziness fatigue/weakness back pain rare but potentially severe cases of hepatic toxicity... 

Similar conclusions were drawn by Blanzat et al. (1984) who studied TbxLai xP50i4, EuxLai xP50i4 and mixed single crystals TbxEui xP50i4 under pressure. By selective excitation of the 5D4 multiplet of Tb3+ the luminescence of Eu3+ could be observed due to an efficient Tb3+ -> Eu3+ energy transfer. Under pressure the lifetime of the Eu3+ luminescence decreased which was interpreted by a weak back-transfer from Eu3+ to Tb3+ due to the increased overlapping of the 5D4 multiplet of Tb3+ with the 5D2 multiplet of Eu3+. 

Importantly, H2 can bind in stable fashion to very electron-deficient metal centers, which are weak back bonders, nearly as well as to more electron-rich M that promote OA. Calculations show that for highly electrophilic M the reduction in back donation is almost completely... 

The general conclusion was that rather weak bonding was established between the cation and the carbon monoxide molecule. The scheme of the bonding was depicted as essentially a transfer of-the carbon lone pair to the cation empty orbitals with a variable extent back-donation from the cation filled orbitals to the antibonding II orbitals of the CO molecule. This bonding scheme generally resulted in an electron deficient carbonyl carbon especially in view of the weak back-donation to the II molecular orbitals of CO. This makes the carbon particularly suitable for nucleophilic attacks by electrophiles. 

We must now distinguish between different techniques. In fine-structure techniques (such as SEXAFS, EAPFS, etc.), weak back-scattering combined with... 

M3. Kemedy for a Weak Back. Take a beefs gall, pour it into 1 pint alcohol, and tmtho frequently. 

I know, Quinn," Lawrence said devoutly. "I was a liability. I was weak back then." He knelt at Quinn s feet, and beamed up at the stem features of the black-robed figure. "But I m not anymore. Now I can help you again. It will be like before, only better. The whole universe will bow before you, Quinn."... 

RVF virus can cause several different disease syndromes. People with RVF typically have cither no symptoms or a mild illness associated with fever and liver abnormalities. However, in some patients the illness can progress to hemorrhagic fever (which can lead to shock or hemorrhage), encephalitis (inflammation of the brain, which can lead to headaches, coma, or seizures), or ocular disease (diseases affecting the eye). Patients who become ill usually experience fever, generalized weakness, back pain, dizzine.ss, and extreme weight loss at the onset of the illness. Typically, patients recover within two days to one week after onset of illne.ss. 

Poor posture can also put stress on back muscles. Poor physical condition can lead to weak back muscles. Drivers should practice a regular exercise program to stretch and strengthen back muscles. 

The sensitivity to get a disk herniation can be genetically predetermined and is called a weak back . This means that the relationship between the spinal vertebrae and the surrounding tissue is insufficient. In most cases a disk herniation occurs because the surrounding muscles are weak and are not able to give adequate protection and support. 

Figure 7. A simple picture of Tolman s x-value. On the left strong back donation to CO leading to a low stretching frequency. On the right weak back-donation to CO leading to a high stretching frequency [5]...

Nucleophilic attack at a ligand is favored when the metal is a weak back bonder, and electrophilic attack when the metal is a strong back bonder. 

Another common model considers the Fischer type as CR bound to L M with weak back donation from two M(d ) orbitals. This leaves a net partial positive charge on carbon as in the Fischer caibene case. On this model, moving to very strong back donation converts the Fischer to the Schrock type with a net partial negative charge on carbon. 

Still, it seems likely that some people just have a weak back. They appear to be prone to back injury. I had mentioned in earlier chapters that I do not believe that nothing can be done to help the team member who appears to be accident prone. I talked about Pete in an earlier chapter. To refresh your memory, Pete was believed by himself and others to be accident prone. In general he would just get hurt a lot. Pete later became focused on safety in the workplace, and his proneness to accidents disappeared. With Pete this proneness to accidents was temporary and was corrected with the right treatment however, I believe that being prone to back injury is different from general accident proneness. 

Obviously the very weak 7t-bonding in transition metal silylenes is the key to imderstand the different bonding properties in transition metal carbenes and silylenes [17, 35], The silylene substituent acts mainly as c-donor and accepts the coordination of additional donor ligands due to the weak back bonding from the transition metal atom. 

The applicable bonding model depends on the strength of the back donation. The Dewar-Chatt (D-C, 5.3) model holds for weak back bonding and the metalacyclopropane (MCP, 5.4) model for strong back bonding. Experimental structures can fall anywhere between the two extremes. For Zeise s salt and other intermediate oxidation state late metals, the D-C model fits best, while for Pt(0), the MCP model applies. Both cases are considered r structures. 

CO binds best to Ni(0) but strong back donation would tend to minimize nucleophilic attack. Ni(II) might be too weakly back-donating to bind CO but if it did, nucleophilic attack would be favored. Ni(I) is midway in properties. 

Dissociative substitution mechanism (Section 4.4) Dewar-Chatt model of M(C=C) bonding involving weak back donation (Section 5.1) Electron configuration (Section 1.4) a-Acceptor and ir-donor metal orbitals (see Section 1.4)... 

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